Wednesday

May 27, 2015

May 27, 2015

Total # Posts: 168

**pre - CALCULUS**

(f ∘ g)(x) = f(g(x)) f(g(x)) = 8(6x - 14) g(x) could be 6x - 14 and f(x) could be 8x
*April 10, 2015*

**algebra**

t = -4 doesn't work for the question you posted there. Is there a bracket missing? I did it both with and without and neither work. I got 3t^2 + 2t + 6 = 6 That then gives me t = 0 or t = -2/3
*April 10, 2015*

**Math**

You're welcome
*April 10, 2015*

**Math**

Starting at 8 keep adding 8s and write out the list of numbers. With 12, start at 12 and keep adding 12s to it and write out that list Once you see the first number that appears in both lists that's the lowest common multiple. Any other numbers that also appear in both ...
*April 10, 2015*

**Mathematics**

Leslie: 4.5 laps = 0.75 hrs x laps = 1.00 hrs Find x (the number of laps Leslie does in an hour) Kayla 3.5 laps = 0.75 hrs y laps = 1.00 hrs Find y (the number of laps Kayla does in an hour) x - y is the difference or extra that Leslie will run in an hour
*April 10, 2015*

**Calculus I**

You want dP/dt, you have dV/dt so what do you need? dP/dt = dV/dt * something the something is dP/dV so that the dVs cancel and so you get dP on top. You have to write PVb=C as P = and then differentiate that to get dP/dV. You should be able to substitute everything in then ...
*April 10, 2015*

**Calculus**

when f'(x) > 0 it's increasing when f'(x) < 0 it's decreasing vertical asymptotes: put the denominator equal to zero and solve for x. So when x^2 - 9 = 0 (Just an extra bit of info: for horizontal asymptotes divide by the highest power of x and then apply...
*April 10, 2015*

**Chemistry**

Well one reason is that the energy of the collision might be lower than the activation energy.
*April 9, 2015*

**Math Check**

The good thing about simultaneous equations is that you can check your own answers by substituting them back into the equations. I just tried that and your answer didn't work for either equation.
*April 9, 2015*

**Trigonometry (identities)**

cos^2(β)-cot^2(β) can be simplified futher. cot = 1/tan = cos/sin
*April 9, 2015*

**Trigonometry**

Change Sin^2(x) into 1-cos^2(x), substitute it in, tidy it up and you'll get a quadratic of the form aCos^2(x) + bCos(x) + c = 0 Then let, say, y = Cos(x) then and you get ay^2 + by + c = 0 which is a more normal quadratic. Solve that for y and put your answer equal to Cos...
*April 9, 2015*

**math**

Use the formula a(n) = a + (n-1)*d for the arithmetic series part. n is the number of the term. E.g. n = 1 is the 1st term, n = 4 is the 4th term, etc. 72 = a + (21 - 1)d You can find a in terms of d. Use that then to get the 1st, 5th and 13th terms in terms of a. See if you ...
*April 9, 2015*

**Math**

Not A Median is the middle number. When you have an even number of data values you have to get the average of the two middle values instead.
*April 6, 2015*

**math**

Pick any three values for x and find the three corresponding values of y for the values you choose. Then right in the form (x,y)
*April 6, 2015*

**physics**

You need an equation of motion v^2 = u^2 + 2aS v = final velocity u = initial velocity a = acceleration s = displacement Watch your units. The velocity is in km/h and your displacement is in cm and you want the answer in m/s^2
*April 6, 2015*

**Math**

*makes the total increase 32.35% not 30% as you have
*April 6, 2015*

**Math**

I see where you went wrong. If, say, you increased the price of something by 20% that's not the same as if you increased the price by 10% today and then 10% again tomorrow. If it was €100 to begin with 10% would be €10. Your total is now €110 If you get 10% ...
*April 6, 2015*

**physics**

conservation of momentum m1u1+m2u2=m1v1+m2v2 m1 = mass of first thing (girl) m2 = mass of second thing (book) u1 = initial velocity of first thing (girl) u2 = initial velocity of second thing (book) v1 = final velocity of first thing (girl) v2 = final velocity of second thing...
*April 6, 2015*

**math**

Real roots would be x = 1 or x = -1 Complex roots would be x = i or x = -i or if the complex number, for example, was 4 - 7i then x = 4 - 7i would be the root if that was the solution to the question.
*April 6, 2015*

**Math**

Not B How do you go from -2 to -12 and from -12 to -72? Is there something you can add/subtract/divide/multiply that would work for both?
*April 6, 2015*

**chemistry**

Universal indicator paper, Phenolphthalein, methyl Orange, pH meter. Mix some with some acid and you should get salt and water. You can use Cobalt Chloride paper to test for water and evaporate to get the salt.
*April 6, 2015*

**maths**

call the number x and make two equations - one from each of the contitions - and put them equal to each other and solve for x
*April 6, 2015*

**Algebra**

F = P(1 + r)^t F = final amount P = Principal amount r = rate (in decimals) t = time
*April 6, 2015*

**math**

It is 6% per quarter though. You don't have to divide by 4. It's not 6% per annum. Even if it was you can't just divide by 4. You have to use P(1+r)^t = P(1+R)^T r = first rate t = 1 (usually) R = second rate T = amount of these time periods in t E.g. 6% AER but I ...
*April 6, 2015*

**math**

Reiny, there are 3 months in a quarter of a year so I'm unsure why you divided by 4 unless you were trying to get the monthly rate but that's not how you get the monthly rate and there aren't 16 months in 4 years. Present value of 1st 2400 is 2400 Present value of ...
*April 6, 2015*

**math**

Option one: $24,000 F = P(1+r)^t F = 24,000(1+0.06)^16 16 because the rate is per quarter of a year and there are 16 quarters in 4 years Option 2: 2400 every quarter for 4 years (so 16 of these 2400 gifts in total) 1st $2400 gift will be in for the full 16 quarters 2nd $2400 ...
*April 6, 2015*

**math**

Oh yeah, I forgot I could simplify too. Thanks Reiny!
*April 6, 2015*

**math**

P(Green) = 5/30 = 1/6 P(yellow after green) = 8/29 (as one has been taken away) Probability of both of these happening - so green and yellow afterwards is multiply the two probabilities together together (1/6)*(8/29) = 8/174 Which is the same as Tia said if simplified
*April 6, 2015*

**Physics**

For part a) Just substitute in t into the equation you have. x = (1.09)cos(3.11πt) x is the displacement and this will come out as an answer in meters. 1.09m is your max amplitute (the number in front of the cos). If you get a negative answer that just means the spring is...
*April 6, 2015*

**physics**

Use F = ma on each mass If you draw it out it helps a great deal as you can fill in all the forces. Gravity acts on both and tension acts on both in the opposite direction to gravity in both cases. The 10kg particle is going to win out so it will fall downwards (the 6kg one ...
*April 6, 2015*

**physics**

Kinetic Energy = (1/2)*m*v^2 maybe? 25,000 = 0.5*m*5^2 Solve for m then.
*April 6, 2015*

**math**

Multiply the numbers. Then use 16 oz = 1 lb to get the units you want I feel like a piece of info is missing like the number of pencils in a box.
*March 30, 2015*

**Pre Algebra**

no, that E-7 means 10^-7 not -10^7
*March 30, 2015*

**math**

oh and then convert the mass from tons into pounds
*March 30, 2015*

**math**

Multiply the two numbers
*March 30, 2015*

**math**

26ft = how many inches Take away the piece of string with no lights (the 16 inches) See what's left and divide by 4 inches (as each light is placed 4 inches apart). Add 1 at the end as you didn't include the first bulb.
*March 30, 2015*

**math**

Find out what length of the string will have lights on it (some of it has no lights on it as said in the question). See how many 4 inches are then in that space. Don't forget to include the first bulb after you work out the total.
*March 30, 2015*

**math**

Ah, but while all rectangles and squares are quadrilaterals not all quadrilaterals are squares or rectangles.
*March 30, 2015*

**math**

Well a square must have 4 equal sides. A rectangle doesn't have to. Following on from Ms. Sue, While you can say a square is always a rectangle, a rectangle isn't always a square.
*March 30, 2015*

**broward**

Find 1 Mol of NaCl (using the periodic table) That amount of g in 1 litre of water is a 1.0 Mol/L solution of NaCl (that is its molarity) Compare that to what you have per litre
*March 30, 2015*

**Math**

Find the two factors using the roots (the intercepts) and then test the point (3,6) in your answer to see if you need to change the sign of everything.
*March 30, 2015*

**math**

You're welcome Jackie. Steve is right about the discriminant being incorrect by the way. x^2 + y^2 = 25 y = x - k x^2 + x^2 - 2xk +k^2 = 25 2x^2 - 2xk + k^2 - 25 = 0 x = 2k +- Sqrt(4k^2 - 4(2)(k^2 - 25)))/4 your discriminant is -4k^2 + 200
*March 30, 2015*

**math**

No, no it asks you for the values of k that let you get 2pts or 1pt or 0pts. You have to solve each of those. E.g. 100 - 4k^2 = 0 100 = 4k^2 25 = k^2 5 = k So, when k = 5 you get only 1 point 100 - 4k^2 > 0 100 > 4k^2 25 > k^2 5 > k So, when k > 5 you get 2 ...
*March 30, 2015*

**math**

if 100 - 4k^2 > 0 then you get 2 points if 100 - 4k^2 = 0 then you get 1 point if 100 - 4k^2 < 0 then you get 0 points
*March 30, 2015*

**physics**

KE = (1/2)*m*v^2 m = mass (in kg) v = velocity (in m/s) Work = Change in KE but it starts at 0 so it's the KE you worked out - 0 Which looks to be the same as the first part and they have the same units too, joules.
*March 30, 2015*

**phusics**

Work = change in Kinetic Energy (units are Joules) KE = (1/2)*m*v^2 m = mass in kg v = velocity in m/s Power = work/time (units are Watts)
*March 30, 2015*

**Chemistry**

Devron is right, I didn't notice the kj added in there instead of j. Your caluclation was correct just off by a factor of 1000 as a result. My apologies for not noticing.
*March 30, 2015*

**Chemistry**

Looks right to me
*March 30, 2015*

**Math**

You have 12/52 for the first choice, 11/51 for the second and 10/50 for the third. Just multiply the three probabilities. MathMate, your instructions are incorrect for the question asked. C(52,12) is the number of combinations of 12 different cards that can be made from 52 ...
*March 30, 2015*

**Math**

probability = (number of favourable outcomes)/(total number of outcomes) total outcomes = 3+6+4 = 13 Question 1: probability tiger = 3/13 then probability bear = 6/12 (as one from the 13 has been picked) then probability dog = 4/11 (as another from the remaining 12 has been ...
*March 30, 2015*

**Math**

k = 5*h It's distance = speed*time See if you can get the rest from there
*February 21, 2015*

**physics**

Use F = ma and v = u + at F = force m = mass a = acceleration v = final velocity u = initial velocity t = time
*February 19, 2015*

**physics**

Equations of motion v=u+at v^2=u^2+2aS S=ut+(1/2)*at^2 u = initial velocity v = final velocity t = time a = acceleration S = displacement. Once you know 3 out of the 5 you can find the other two. See if you can write down 3 things you know about the situation.
*February 17, 2015*

**English - Please read.**

One epic simile is: "I leaned on it turning it AS a shipwright turns a drill in planking, having men below to swing to two-handled strap that spins it in the groove." Comparing the turning of the spike into the creatures eye to a shipbuilder using a drill. The other ...
*February 17, 2015*

**College Algebra**

You're almost there. Tidy up the equation to get: 16t^2 - 96t + 128 = 0 which simplifies to t^2 - 6t + 8 = 0 Now you have a simple quadratic. You'll get two answers because there are two times when it reaches 228ft.
*February 17, 2015*

**math - ans.check**

In your one troy, -17.1428.. = 45 - x then by subracting 45 from both sides you get -17.1428.. - 45 = - x -62.1428.. = - x Multiply both sides by -1 Then x = 62.1428 which is what kudum had (62 and 1/7)
*February 17, 2015*

**Calculus**

typo in the curved area. Sould be pi*r^2 not pi^r^2 Same in the cost equation
*February 17, 2015*

**Calculus**

Volume: V = pi*r^2*h = 60 h = 60/(pi*r^2) Area: Area of lid = pi*r^2 Area of Curved area + bottom = pi^r^2 + 2pi*r*h Put the h we worked out in terms of r into the area equation. Cost = 0.50*(pi*r^2) + 1.50*(pi^r^2 + 2pi*r*[60/(pi*r^2)] Tidy up a little and then differenciate ...
*February 17, 2015*

**GEOMETRY**

Pythagoras theorem hyp^2 = b^2 + c^2 where b and c are the other two sides As it is a triangle with two 45 degree angles then b and c would be the same. In this case, P So you get hyp^2 = P^2 + P^2 See how you get on with the question now.
*February 17, 2015*

**math**

Each DVD he watches instead of going to the cinema saves: $12.50 - $1.95 = $10.55 So how many $10.55s are there in $125?
*February 17, 2015*

**calculus A**

e) Substitute t = 8s into S = t^3 -12t^2 + 21t i) Speeding up = acceleration > 0 when is a > 0? It's when 6t - 24 > 0 Slowing down = acceleration < 0 (just as extra info: constant speed would be when your acceleration = 0)
*February 17, 2015*

**Math**

diesel = 2*petrol 1) d = 2p 2) d + 2p = total sold = 900,000 See if you can find p and d from those two equations now and then the profits after that.
*February 17, 2015*

**Physics**

Well you need to use the equations of motion v=u+at v^2=u^2+2aS and S=ut+(1/2)at^2 a = -g in this question What happens first is the bag moves upwards for a short time (as it has a velocity of 1.45m/s) and then falls down You can do this question in one go (instead of working ...
*February 2, 2015*

**science 7th**

The density of something doesn't change if you cut it in half or do things like that to it. For example, a litre of water has the same density as a glass of water (as long as they are at the same temperature). It's a property of the material. Also, the unit of density ...
*February 2, 2015*

**math**

Spot on :)
*February 2, 2015*

**Physics**

Situation 1: u = v1 v = 0 m/s a = -g = -9.81m/s^2 S = y1 use S = ut+(1/2)*at^2 to get y1 in terms of v1 Situation 2: u = 1.27v1 v = 0 m/s a = -g(saturn) = -0.145m/s^2 S = y2 use S = ut+(1/2)*at^2 to get y2 in terms of v1 Then use the two answers together to get y2 in terms of y1
*February 2, 2015*

**Math**

$129.00 = 105.75% of the price before the sales tax was added Find what would = 100% That answer is then = 123% of the price before the price increase Find what price = 100% again and that'll be the original price before the increase and before the tax was added
*February 2, 2015*

**Math**

Elis = y Samuel = Elis - 10 David = Elis + 20 Total = 140 See if you can find y now. Although looking at it it's not an whole number which is strange..
*January 31, 2015*

**Physics**

Use Pythagoras' Theorem
*October 26, 2014*

**Algebra**

since you can't get the square root of a negative number find when 6-x-x^2 < 0 It's a quadratic that you can solve. Plot it and see where the graph is above the x-axis. The domain is the possible x-values that give y-values greater than or equal to 0.
*October 26, 2014*

**physics**

You have to use F=ma and draw a force diagram for each person. For the person hanging down F = ma 83*g - T = 83*0 (you don't want it to accelerate) (T = tension in the string) For the person standing on top. F = ma T - Ff = 101*0 (Ff = force of friction = (mu)*R where mu ...
*October 26, 2014*

**eng**

Maybe you saw the plane crash and went over to help and you find two people alive but are both bleeding badly and will die in minutes. Who do you help? Why not the other person? or Maybe you were on a plane and there were hijackers and you were making a choice. You want to ...
*October 26, 2014*

**Physics**

edit: m1u1 + m2u2 = m1v1 + m2v2 I had a small error in the previous post with that formula.
*October 26, 2014*

**Physics**

Write two equations of conservation of momentum m1u1 + m1u2 = m1v1 + m2v2 One in the i direction (West to East) One in the j direction (South to North) v1 = v2 in both cases (i and j) because they stick together afterwards. For example: Velocity of the 1300kg car is 0i + 27j ...
*October 26, 2014*

**Algebra 2**

differentiate y with respect to x (dy/dx). That gives you the slope at any point on the graph. The slope is always 0 at the max and min points so put dy/dx = 0 and solve for x. Once you get that value of x put it back into y to find the corresponding y value for the minimum ...
*October 22, 2014*

**Physic**

Cliff height is correct Max height is correct (I got 29.7m) Ball's impact speed isn't right. you need to find Vx and Vy at time 3.3s Vx = Ux - 0*t (gravity doesn't act in the horizontal direction) Vy = Uy - g*t (gravity acts downwards so -ve g) So we get Vx = Ux = ...
*October 22, 2014*

**math**

Not C either. 10^2 + 7^2 = hyp^2 Find the hyp from that
*October 22, 2014*

**math**

41^2 = 40^2 + x^2 1681 = 1600 + x^2 81 = x^2 9 = x
*October 22, 2014*

**math**

Careful Brady. In this question it's 41^2 = 40^2 + x^2
*October 22, 2014*

**math**

Afraid not.
*October 22, 2014*

**Science ONE QUESTION!**

Spot on :)
*October 22, 2014*

**Science ONE QUESTION!**

Ok, so if it was 100 kg m/s before then according to the conservation of momentum it must be...
*October 22, 2014*

**guidance**

Discipline could have the opposite effect. Choices is the correct answer. By making your own decisions you take ownership of them and shape your life. Constant care can make you overly reliant on others.
*October 22, 2014*

**Math**

vol of a sphere = (4/3)*pi*r^3 = 2404*pi find r from that. The length, width and height of the box around the sphere will be the diameter of the ball. Diameter = 2r Area of box = 6*(2r)^2 = 24r^2 cm2 (6 identical faces of area 2r*2r)
*October 22, 2014*

**Math**

Well, what % of is money does he have now? i.e. what percentage does $120 equal? What percentage do you want? You'll get something that looks like this example: 10% = $70 (what you were given) 50% = ? (what you want) What would 50% be in dollars in that example? See if you...
*October 3, 2014*

**Science**

You're welcome!
*October 2, 2014*

**Science**

It's adding if the forces are in the same direction. If you had 30 people on one side of the box and then 20 more joined them. You would have 50 people pushing in one direction. If you had 30 people on one side of the box and 20 on the opposite side then you would be the ...
*October 2, 2014*

**Science**

Imagine 15 people pushing a box in one direction and 10 people on the other side pushing against them. If you had 1 person each side pushing against each other would it move? What do you think the answer is?
*October 2, 2014*

**Science**

edit: my reply before was to your reply of 'B'? A nonzero force just means a force. It means that 0N isn't allowed as that wont affect anything. It's not D either I'm afraid. Damon said the correct answer there.
*October 2, 2014*

**Science**

Afraid not, try again. You can't have a force greater than the reaction force as Newtons 3rd Law states that 'Every action has an equal and opposite reaction'. Imagine kicking a wall. If you kick it gently your foot doesn't feel much of a force back but if you ...
*October 2, 2014*

**Science**

Imagine a football stationary on the ground or even moving through the air. You then apply a nonzero force (i.e. you kick it) What happens?
*October 2, 2014*

**physics**

Ignore the 2nd half of the question at first (the player 48.5m away). You need to find the range of the football. Work that out first. After that compare that distance to where the player is. i.e. find the distance between where the ball lands and 48.5m. Then remember that the...
*October 2, 2014*

**Physics wavelength question, help please .**

You're welcome :) Remember, the higher the frequency the higher the energy. That's why we have Blu Ray players and not Red Ray players.
*October 2, 2014*

**Physics wavelength question, help please .**

Use these E = hf Energy = Planck's Constant x frequency c = fλ Speed of light = freq of the light * wavelength of the light
*October 2, 2014*

**Math**

What do you think the answers are first?
*October 2, 2014*

**Vectors problem help?**

ahh ok. well, |A| = sqrt[ (3)^2 + (6)^2 + (-2)^2 ] -ve signs don't affect the length of the vector. That only tells you about the direction of it. |A| = sqrt[ 9 + 36 + 4 ] = sqrt [49] = 7 The length of the vector is 7. Unit vectors have length 1. So we need to divide A by ...
*October 2, 2014*

**Vectors problem help?**

Unit vector = V/|V| if V = ai + bj + ck |V| = sqrt(a^2 + b^2 + c^2) = length of the vector
*October 2, 2014*

**Physics**

Magnitude of a vector is its length: if v = ai + bj + ck |v| = sqrt(a^2 + b^2 + c^2) So that's the length. It's a scalar quantity. |b| = sqrt(16+4+4) = sqrt(24) |v| = |b| Parallel vectors: the dot product is 0. so. A.v = 0 or 2a + 3b - 1c = 0 The thing is there isn'...
*October 2, 2014*

**Math**

An interval is like a range. An interval could be from 3 to 8 for example which would be all the numbers between 3 and 8 inclusive. What is the context?
*October 2, 2014*

**Math--4 practice questions?**

What do you think the answers are first? I like to think of these as money. Imagine the first one there is you had €27 in your hand, something happened to it and now you have €21. So, what happened? Was money added or taken away? How much was added or taken away?
*October 2, 2014*