Saturday

November 28, 2015
Total # Posts: 35,839

**Math**

well, it has to double three time to be full, right?
*October 9, 2015*

**math**

well, 20 = 4*5 25 = 5*5 So, what do you think?
*October 9, 2015*

**Math**

not quite. 6 pizzas makes 48 slices 3 1/4 pizzas are 26 slices. So now, how many slices were left over? How would you interpret Janet's suggestion?
*October 9, 2015*

**pre calculus**

well, just plug in k and k+1 for n. You need to prove that if Sk is true, then Sk+1 is also true. Then, if you can show that S1 is true, then S2,S3,... are all true as well. 1+4+...+(3k-2)+(3(k+1)-2) = Sk+3(k+1)-2 = k(3k-1)/2 + 3(k+1)-2 = (k(3k-1) + 6(k+1)-4)/2 = (3k^2-k+6k+6-...
*October 8, 2015*

**math**

how much did each eat? Heck, they told you that. Convert each fraction to decimal to compare. 0.5 is 1/2. 2/3 = 0.666 and so on
*October 8, 2015*

**Math**

The one-digit factors of 54 are 1,2,3,6,9 so, which three of those add to 14?
*October 8, 2015*

**Science**

All the energy ultimately comes from the sun.
*October 8, 2015*

**trig**

nice formulas. Is there a question in there somewhere?
*October 8, 2015*

**math**

you want to add some parentheses, or at least some spaces, so we can work with that? As written, using the normal order of operations, you have 4-x^2/x^2+7x+12/2x-4/x+3 4-1+7x+6/x-4/x+3 3+7x+2/x+3 6 + 7x + 2/x I doubt that is what you had in mind.
*October 8, 2015*

**algebra**

enter your polynomials at http://calc101.com/webMathematica/long-divide.jsp and see all the details
*October 8, 2015*

**geometry**

assuming RST are collinear points, in that order, RS+ST=RT, so hmmm. If R bisects ST, and 5x=7 is a typo for 5x+7, then since SR=RT, 5x+7 = 15x-1 10x = 8 x = 4/5 But you may have had other things in mind. Remember, we cannot see what diagram you have in front of you. Nor can ...
*October 8, 2015*

**Pre Calculus**

(a) if you mean (3f+2g)(1) then that is 3f(1)+2g(1) = 3*50 + 2(-5) = 140 (f◦g)(-1) = f(g(-1)) = f(-3) = 10 f(x) = x^2 g(x) = x/(x+4) h(x) = g◦f = f/(f+4) = x^2/(x^2+4)
*October 8, 2015*

**math**

see related questions below
*October 8, 2015*

**math**

pick any five values for x. Multiply each by 18. Plot those points. Can you see what a useless exercise it is for you to ask us to plot a graph and verify it? Sheesh.
*October 8, 2015*

**Math**

one-digit factors of 54 are 1,2,3,6,9
*October 8, 2015*

**Math**

Let 2x be the least. Then the next 3 even integers are 2x+2, 2x+4, 2x+6 So, add them up: 2x + 2x+2 + 2x+4 + 2x+6 = 2x Now solve for x, and ... Extra credit: We used 2x to make sure it was an even number. What would have happened if we had just used x instead?
*October 8, 2015*

**Pre-Calc**

the same way you would simplify 2/3 + 3/2. Put it all over a common denominator: tan/(1+sec) + (1+sec)/tan = [tan^2 + (1+sec)^2]/(tan(1+sec)) = (tan^2 + 1+2sec+sec^2)/(tan(1+sec)) = (sec^2-1+1+2sec+sec^2)/(tan(1+sec)) = (2sec^2+2sec)/(tan(1+sec)) = 2sec(1+sec)/(tan(1+sec)) = ...
*October 8, 2015*

**Math Help**

oh, please...
*October 8, 2015*

**Math (Quadratics)**

You'll need to use the quadratic formula on that one. Or, completing the square, 8x^2+2x-4 = 0 8(x^2 + x/4) = 4 8(x^2 + x/4 + 1/64) = 4 + 8/64 8(x + 1/8)^2 = 4 + 1/8 (x + 1/8)^2 = 33/64 x + 1/8 = ±√33 / 8 x = -1/8 ±√33/8 x = (-1±√33)/8
*October 8, 2015*

**Algebra i need serious help**

Sorry, I only give jocose help. Since 3-x = -(x-3) |x-3| = |3-x| for all values of x
*October 8, 2015*

**Division need help urgently plz**

all you want is the last digit. So, look at the powers of 7: 7^1 = 7 7^2 = 49 7^3 ends in 3 7^4 ends in 1 since 3*7=21 913 = 4*228 + 1 So, 7^913 = 7^4^228 * 7 thus, it ends in 7
*October 8, 2015*

**Algebra 2**

try using ^ for powers. That is y^3 means y cubed. The formatting has messed things up to where they are incomprehensible.
*October 8, 2015*

**Physics**

220 km/hr = 2.20 * 10^5 m/hr So, there must be a headwind of 2.8-2.2 = 0.6 * 10^5 m/hr. That is, a wind blowing north at 60 km/hr
*October 8, 2015*

**Math**

paycheck: x food: 1/6 x, leaving 5/6 x house: 3/5 of 5/6 x = 1/2 x, leaving 1/3 x bills: 1/3 of 1/3 x = 1/9 x, leaving 2/9 x entertainment: 1/4 * 2/9 x = 1/18 x, leaving 1/6 x so, 150 = 1/6 x x = 900
*October 8, 2015*

**math please help!!**

the graph is concave down where 16e^-x^2 (2x^2-1) < 0 that is where 2x^2-1 < 0 x^2 < 1/2 so, f is concave down on the interval (-1/√2,1/√2)
*October 8, 2015*

**Math 125**

It appears that the number of calculators sold, as a function of the amount of discount (x) is p(x) = 10000+400x so, just plug in x=20 for the demand at $75.
*October 8, 2015*

**Calculus**

∫[0,8] 8x-x^2 dx = 4x^2 - 1/3 x^3 [0,8] = 4*8^2 - 1/3 * 8^3 = 256 - 512/3 = (768-512)/3 = 256/3 Maybe you should have shown your work.
*October 8, 2015*

**Mathematics(XI)**

google is your friend: https://answers.yahoo.com/question/index?qid=20121228030540AAIm82k
*October 8, 2015*

**math**

since √y = 7-x, √x + (7-x)^2 = 11 √x = -x^2+14x-38 x = x^4-28x^3+272x^2-1064x+1444 x^4-28x^3+272x^2-1065x+1444 = 0 (x-4)(x^3-24x^2+176x-361) = 0 good luck with the cubic. But, if x=4, y=9
*October 8, 2015*

**Find x algebra help**

no easy algebraic way to do this. However, with a little thought, you should be able to come up with 3^2-1 = 2^3
*October 8, 2015*

**Pre-Calculus**

well, just plug in the values: f(x)-f(1) = (-3x+2)-(-3*1+2) = -3x+3 Now divide by x-1 and you have (-3x+3)/(x-1) = -3(x-1)/(x-1) = -3 For the other, the same thing: f(x+∆x)-f(x) = 2(x+∆x)-2x = 2x+2∆x-2x = 2∆x Now divide by ∆x and you have 2∆...
*October 8, 2015*

**math**

a < b x >= y etc. If you have some specific questions, it would be a bit more useful to see how they can be answered.
*October 8, 2015*

**Algebra**

Looks like 9!-1 to me. Now, if you want (9!-6!)/(9-3)! that's 503. What is that supposed to model?
*October 8, 2015*

**Math**

If the faster person takes x hours, then the slower person takes (x+1) hours. So, how much of the job gets done in an hour? 1/x + 1/(x+1) = 1/5 Now just find x.
*October 8, 2015*

**Calculus 1**

the light turns through angle θ where dθ/dt = 4π. If the light hits x km away from P, then x = 4tanθ So, knowing that tanθ = 1/4, plug in the numbers and find dx/dt: dx/dt = 4 sec^2(θ) dθ/dt
*October 8, 2015*

**calculus**

I'll let you do the discussion. You just need to recall that f' = x^3 - 3x f" = 3x^2 - 3 f is increasing where f' > 0 f is concave up where f" > 0 f has max/min where f'=0 f has inflection where f" = 0
*October 8, 2015*

**Geometry**

as with the supplementary angles problem, 4x = (90-x)+10
*October 8, 2015*

**Geometry**

two angles are supplementary if they add to 180. So, if one angle is x, the other is (180-x), and you have 2x = (180-x)-36 2x = 133-x 3x = 144 x = 48
*October 8, 2015*

**Calculus 1**

If the hands are separated by an angle θ, then using the law of cosines, the distance z between the tips is z^2 = 6^2 + 9^2 - 2(6)(9) cosθ The hour hand rotates at a speed of 2π/1440 radians/min, and the minute hand moves at 2π/60 radians/min. So, figure &#...
*October 8, 2015*

**Calculus 1**

at the moment in question, we have a 6-8-10 triangle. You know that tanθ = y/x = √(100-x^2)/x or, x tanθ = √(100-x^2) So, tanθ dx/dt + x sec^2θ dθ/dt = -x/y dx/dt Now just plug in your values to find dθ/dt
*October 8, 2015*

**Calculus 1**

You know that when the water has depth y, the surface of the water has radius (4/6)y So, at depth y, the volume of water is v = π/3 r^2 y = π/3 (4/9) y^3 dv/dt = 4π/9 y^2 dy/dt That's if no water is draining out. SO, adjust dv/dt when you get your answer above.
*October 8, 2015*

**math**

amt = ears/3
*October 8, 2015*

**HELP HELP CALCULUS**

u=5e^x u' = 5e^x y = e^u y' = e^u u' = e^(5e^x) * 5e^x or, y' = 5e^(x+5e^x) y" = 5(1+5e^x)e^(x+5e^x)
*October 7, 2015*

**Geometry**

I've solved this one ---thanks
*October 7, 2015*

**Geometry**

find the image, of o(-2,-1) after two reflections first across the line y=-5 and then across the line x=1
*October 7, 2015*

**Math**

well, geez -- get rid of the parentheses and collect terms! 4+2(x+5) / 14-2(x+5) = 4+2x+10 / 14-2x-10 = 14+2x / 4-2x = (7+x)/(2-x)
*October 7, 2015*

**Math**

v = pi r^2 h so, find h when pi*18^2 h = 31000
*October 7, 2015*

**math**

rearrange to y = 3x-6 That is called the slope intercept form. I suspect you can now tell the slope, eh? For the y-intercept, just set x=0 and find y.
*October 7, 2015*

**algebra**

(9^2)^p = 9^(2p) so, 2p = 8
*October 7, 2015*

**algebra**

3^5 = 243 Just going that far, you can see that none of the choices will do. I suspect a typo in your presentation.
*October 7, 2015*

**math**

I'll assume you mean (x+160)/5 = 2/(3x-2) (x+160)(3x-2) = 10 3x^2+476x-330 = 0 Now you can use the quadratic formula. If that's not what you meant, how about some parentheses to clarify the grouping?
*October 7, 2015*

**algebra**

(2.8 * 10^7)/(1.4 * 10^3) = (2.8/1.4)*10^(7-3) = 2.0*10^4
*October 7, 2015*

**ALGEBRA**

I think you'd do well to review your scientific notation. Any explanation I give here will just be a duplication of what you have already (I hope) read.
*October 7, 2015*

**ALGEBRA**

14,200,000 10,700,000 ---------------- 24,900,000 = 2.49x10^7 or, 1.42x10^7 + 1.07x10^7 = 2.49x10^7
*October 7, 2015*

**ALGEBRA**

3^2 * 3^-5 = 3^(2-5) = 3^-3 = 1/3^3 Your notation is very sloppy.
*October 7, 2015*

**algebra**

x = ±√20
*October 7, 2015*

**Math**

direct: y=kx or x=ky inverse: xy = k where k is a constant. So, check 'em out.
*October 7, 2015*

**math**

102 = 96*1.0625 So, 102 is 6.25% larger than 96
*October 7, 2015*

**Algebra 2**

an expression has no solution. An equation has a solution. Plugging in x = -9/4 results in a value of 3/56. Not sure whether that's what you want. Leaving in x as-is, the expression evaluates to (-3x-6)/14
*October 7, 2015*

**Alg2.**

what, you can't check it? Apparently not. In fact, your results row should be 4 -2 -1 1/2 7/4 25/8
*October 7, 2015*

**Calculus**

I think you mean y = √(11x + √(11x+√(11x))) y^2 = 11x + √(11x+√(11x)) If u^2 = 11x, u' = 11/(2√(11x)) y^2 = u^2 + √(u^2+u) 2y y' = 2u u' + (2u+1)u'/(2√(u^2+u)) 2y y' = u' (4u+1)/(2√(u^2+u)) Now ...
*October 7, 2015*

**Algebra**

Rotating 90° about the origin takes P:(x,y) -> P':(-y,x) So, plug in your numbers.
*October 7, 2015*

**Algebra**

A segment with endpoint a(3,1) and b(-1,-1) is rotated 90 degrees about its origin what are the new of a and b prime?
*October 7, 2015*

**math**

1000 * 1.05^18
*October 7, 2015*

**Algebra**

just solve for x when h=0. Clearly, it is only when x=0. If you mean h(x)=-32x^2/(140^2+x) If you meant it as written, h(x)=-32x^2/140^2 + x = x(1 - 64x/1225) h=0 when x = 1225/64
*October 7, 2015*

**Please help with MATH**

been there, done that. http://www.jiskha.com/display.cgi?id=1444251037
*October 7, 2015*

**Geometry**

Each quadrant contains 90°, starting from 0°. QI is 0-90° QII is 90-180° Or, going the other way, QIV is 0 to -90° QIII is -90 to -180° So, now what do you think?
*October 7, 2015*

**Geometry**

You are correct. An angle has its own measure, regardless of whether it is anywhere near another angle.
*October 7, 2015*

**Math**

assuming she answered all the questions, and got x wrong, then there were (50-x) correct. 2(50-x) - x = 85 Now just find x.
*October 7, 2015*

**Algebra 2**

you know the possible roots are ±8,±4,±2,±1 So, look for the easy ones first, using synthetic division. It's easy to find that there are no rational roots.
*October 7, 2015*

**math**

well, how many hours in a day? -42.4 * 24
*October 7, 2015*

**Math**

there is a 1/3 chance of rolling a 3 or a 5. So, 1/3 of the time, you are likely to get that. What is 1/3 of 260?
*October 7, 2015*

**Algebra**

p(x) = 25x-500
*October 7, 2015*

**Math**

No idea. I can't quite even figure just what the question is. It appears you are working on multiplying fractions. 1st model: 7/20 2nd model: (7/20)(6/7) = (7*6)/(7*20) = 3/10 3rd model: (7/20)(27/35) = (7*27)/(20*7*5) = 27/100 4th model: (7/20)(4/5) = (7*4)/(20*5) = 7/25
*October 7, 2015*

**Math**

If you're taking square roots, the number must be a perfect square to give a rational root. 64 = 8^2, so √64 = 8 is rational Similarly, since 64 = 4^3, ∛64 = 4 is rational. For small numbers, it's easy to check for possible roots, as there aren't that ...
*October 7, 2015*

**math**

40 men @ 8 hrs/day = 320 man-hrs/day 60 men @ 6 hrs/day = 360 man-hrs/day So, it will take 320/360 = 8/9 as long, or 80/3 days
*October 7, 2015*

**Calculus 1**

for a sphere, a = πd^2 da/dt = 2π dd/dt -6 = 2π*11 dd/dt So, dd/dt = -3/(11π) cm/min
*October 7, 2015*

**math**

3+4+5 = 12 360 = 12*30 that should help
*October 7, 2015*

**math**

first off, what is standard form? Those look pretty standard to me already.
*October 7, 2015*

**physics**

s = 3.2t + 1/2 at^2 3.2(3.3) - a/2 (3.3^2) = 16 a = 1.0 so, a = 1/9.8 g So, sin(theta) = 1/9.8 theta = 5.86 degrees
*October 7, 2015*

**math**

well, the sets of three factors of 48 are 1,1,48 1,2,24 1,3,16 1,4,12 1,6,8 2,2,12 2,3,8 2,4,6 3,4,4 Looks like the 10th student will have to duplicate one of those solids.
*October 7, 2015*

**Calculus**

Okay. If the man is x meters from the pole, and his shadow's length is s meters, then using similar triangles, we have (x+s)/5 = s/1.7 So, that means that x = 5s/1.7 - s or, s = 0.51x So, ds/dt = 0.51 dx/dt = 0.51*1.6 = 0.82 m/s
*October 7, 2015*

**Simultaneous equation**

well, using the values 1,3,5 how can you make them add up to 1 if not all are positive?
*October 7, 2015*

**Simultaneous equation**

well, if we want integer solutions, it is clear that not all the values can be positive. However, squares are positive, and we know that 1^2+3^2+5^2 = 35 You will need to make one or two of the variables negative, so you sum to 1, but that should work for the cubes as well.
*October 7, 2015*

**MATH HELP PLEASE**

k(x) = (x−1)^2 − 6 Clearly the vertex is at (1,-6), The x-intercepts are not integers, The y-intercept is at (0,-5) So, pick any integer value except 0 or 1 for x, and plug it in! k(-1) = -2 k(10) = 75 k(-100) = 10195 You can use decimal or irrational values as ...
*October 7, 2015*

**6th Grade Math**

If there were x boxes at $2, the rest (35-x) were $3 boxes. So, add up the sales for everything: 2x+3(35-x) = 92
*October 7, 2015*

**math**

since the relationship is proportional, the distance d and the time t are related by d = kt where k is a constant. So, if you double the time, you have k(2t) = 2(kt) = 2d so, the distance also doubles. Or, you can think of it like this. d/t = k, a constant If you now have 2t, ...
*October 7, 2015*

**Algebra**

Well, you did some calculations (some of them incorrect), but at the end, you didn't even come close to answering the question that was asked. k(x) = (x−1)^2 − 6 Clearly the vertex is at (1,-6), The x-intercepts are not integers, The y-intercept is at (0,-5) So...
*October 7, 2015*

**Math**

if the differences are constant, the sequence is arithmetic. They are 1,2,3,4 So, the sequence is not arithmetic. If the ratios are constant, the sequence is geometric. They are 3/2, 5/3, 8/5, 3/2 So, the sequence is not geometric either.
*October 7, 2015*

**math**

0x3 + 18x1 1x3 + 15x1 2x3 + 12x1 ... 6x3 + 0x1
*October 7, 2015*

**maths**

(6/2)(2a+5d) = 6 (a+d)(a+4d) = -80 or, 2a+5d = 2 a^2+5ad+4d^2 = -80 Now just solve for a and d. One sequence is -14, -8, -2, 4, 10, 16 sum = 6 (-8)(10) = -80 There is another value for a as well
*October 7, 2015*

**Angle of depression need help also**

if the angle of depression is decreasing, then the plane is flying away from the platform. 30s * 600km/hr * 1hr/3600s = 5km So, if you draw a diagram, you can see that if the plane's height is h km, h cot45° - h cot60° = 5
*October 7, 2015*

**What must be added maths need help**

if the needed amount is z, then x/y + z = y/x z = y/x - x/y You can massage that into other forms if you like. Not sure why this caused you trouble. If I ask what needs to be added to 6 to make 10, you naturally say 10-6 = 4 right?
*October 7, 2015*

**Maths**

cubics are not simple to solve, in general. Descartes' Rule of Signs says that there are no negative roots. I suggest a graph or Newton's method for finding the roots. What methods have you studied? f(0) = -2.4 f(1) = 3.49 f(3) = 3.0 f(4) = -0.9 f(10) = -1.08 f(11) = ...
*October 7, 2015*

**Calculus 1**

after t hours, car One has traveled 40t miles car Two has traveled 30t miles Using the Pythagorean Theorem, the distance between the cars is 50t miles. Looks like the distance is growing at a constant 50 mi/hr. No calculus even needed.
*October 7, 2015*

**algebra**

the values to be excluded from the domain are those which make the denominator zero, since division by zero is undefined. so, where is 8x(x-1) = 0?
*October 7, 2015*

**Math**

so, how does your chart look? I assume you have bands of various widths, in various colors.
*October 7, 2015*

**Holy Batman!**

40000*1.16^3
*October 6, 2015*

**Math**

where is 8x^2-8x = 0?
*October 6, 2015*