Saturday

August 30, 2014

August 30, 2014

Total # Posts: 24,501

**Algebra**

log0.900.6 - log0.850.6 = 1.7 or, since you probably don't have a button for log0.9x, log(0.6)/log(0.9) - log(0.6)/log(0.85) or even log(0.6)(1/log(0.9)-1/log(0.85))
*July 14, 2014*

**Geometry**

I didn't see where the solid was a pyramid. Usually a prism is a right prism, so the v = (area of base)*height
*July 14, 2014*

**science**

Name it analogously with table salt, which is Sodium Chloride. That -ide suffix indicates that there are just the two elements. Ever heard of the ointment Zinc Oxide? Same deal.
*July 14, 2014*

**math**

the x-coordinate is halfway between the two end x-values: (-3 + -8)/2 = -11/2 Do the y-value the same way.
*July 14, 2014*

**math**

after n cuts, the thickness is 0.1 * 2^n mm. so, evaluate when n=30.
*July 14, 2014*

**algebra**

just solve for t when the height is zero: -16t^2 + 112t + 128 = 0 just a normal quadratic equation.
*July 14, 2014*

**Alegbra**

how many times is this going to be posted? Review the point-slope form of a line: a line with slope m, through the point (h,k) has the equation y-k = m(x-h) So, look at the equation above, and read off m and (h,k)
*July 14, 2014*

**Alegbra**

The point is clearly (-5,4) Now since the slope is 3/2, a second point is up 3 and right 2.
*July 14, 2014*

**Trigonometry**

just figure s(5)-s(1)
*July 14, 2014*

**physics**

The tank weighs the same, regardless of its contents. Figure the volume of material, and multiply that by the material's density. :-)
*July 14, 2014*

**physics**

figure the volume: .18 * .78 * .44 m^3 now multiply that by the density, in kg/m^3
*July 14, 2014*

**Pre algebra**

(5*62 + 50)/6
*July 14, 2014*

**math**

let the numbers be x-1,x,x+1 The sum is 3x = 39 so, the middle number is 13
*July 14, 2014*

**Math**

log740353607 = log40353607/log7 = 9 so, 40353607 = 7^9
*July 14, 2014*

**math**

x = 2^(1/2) since log √x = 1/2 log x, log x = -2 x = 10^-2 lnx = ln(e*(x+1)) x = e*(x+1) ...
*July 14, 2014*

**Physic**

1W = 1J/s 1 kwh = 1000 Wh = 1000J/s * 3600s/h
*July 14, 2014*

**Math**

(9+1)/(9+1+6)
*July 14, 2014*

**physics**

750 + 750 + 625
*July 14, 2014*

**Calculus 2**

actually, the integral isn't so bad if you recognize that the integrand is just x^4 + 1/x^4 http://www.wolframalpha.com/input/?i=arc+length+of+x^5%2F10%2B1%2F%286x^3%29+from+3+to+6
*July 14, 2014*

**Physics**

well, you have the mass of 1 liter. So, what is the mass of 2 liters? Now just look up the conversion factor for kg to lb. A handy site is http://www.onlineconversion.com/weight_common.htm On the home page there, you can find many other conversion calculators.
*July 14, 2014*

**mqr/117**

rewrite f(x) as 5(x + 3/10)^2 + 11/20 and then you can just read off the coordinates of the vertex.
*July 13, 2014*

**Math**

you want the set of elements common to your two sets. So, which numbers are in both lists?
*July 13, 2014*

**Math**

The number of people taking something is 23+32-9 So, that leaves how many taking nothing?
*July 13, 2014*

**Alegbra**

They are perpendicular if the product of their slopes is -1. So, is (-7)(-7) = -1 ?
*July 13, 2014*

**Math**

think of the calendar as units of 24 hours So, 5:44 am on day 10 is the same as 29:44 on day 9. So, subtract 14 from 29 and you have 15:44 of the previous day, or 3:44 pm. Or, you could just subtract 24 hours, giving you 5:44 am of the previous day. But you only wanted to ...
*July 13, 2014*

**Alegbra**

If you mean y = -3/2 (x+5) you can see easily that y=0 when x = -5. So, that's where the graph crosses the x-axis. Now, since the slope -s -3/2, just mark a second point, 3 down and 2 to the right from there. Join those two points with a line, and that's the graph.
*July 13, 2014*

**math**

I'd say that would be 17+3=20 assuming the ladder is laid vertically against the wall -- an unusual placement, to be sure.
*July 13, 2014*

**math**

the grade would be 15/5280 = 0.284%
*July 13, 2014*

**Math 221**

as with most problems involving fractions, work first with the denominators. They cannot be added or subtracted unless they all have the same denominator. 5/12 + 7/9 The GCD(12,9) = 36. So, what you have is 15/36 + 28/36 Now all the "units" are the same. Just as you ...
*July 13, 2014*

**maths - oops**

Err, I mean one leg=2. So half the chord has length √21
*July 13, 2014*

**maths**

Draw a diagram, including the radii to the ends of the chord. Draw the radius perpendicular to the chord. You now have two right triangles with one leg=1 and hypotenuse=5. Half the length of the chord is √24.
*July 13, 2014*

**Algebra II**

no, since 2x^2+x-15 = (2x-5)(x+3) Just multiply both sides by (2x-5)(x+3) The thing to watch out for is to be sure to note that 5/2 and -3 must be excluded from the domain.
*July 13, 2014*

**mat/117**

you want where P < 0 P(x) = 750x(20-x) You know that P=0 when x=0 or 20 Since the graph is a parabola opening downward, P>0 between the roots. So, P<0 if x>20
*July 13, 2014*

**mat/117**

translating upward just means add 11 to g.
*July 13, 2014*

**mat/117**

f(x) = -5(x - 3/10) + 29/20 If that doesn't tell you the answer, review your forms of quadratics.
*July 13, 2014*

**mat/117**

(fg)(x) = f(x)*g(x) = (-6x-1)(4x^2)
*July 13, 2014*

**mat/117**

(f+g)(x) = f(x) + g(x) so, just add the two polynomials together.
*July 13, 2014*

**phi 208**

life is like a simile.
*July 13, 2014*

**Math**

ok. now what?
*July 13, 2014*

**math**

Surely this treated in your text. You want A/(v-1) + B/(v+2) = 1/(v-1)(v+2) A(v+2) + B(v-1) = 1 Av + 2A + Bv - B = 1 (A+B)v + (2A-B) = 0v + 1 For those polynomials to be identical, all of the coefficients must match. So, we have A+B = 0 2A-B = 1 solve those and you get A = 1/3...
*July 12, 2014*

**math**

You use partial fractions. 1/(v+2)(v-1) = 1/3 (1/(v-1) - 1/(v+2))
*July 12, 2014*

**science**

light is reflected from both sides of the glass.
*July 12, 2014*

**algebra**

set x=0 and evaluate y. That's the y-intercept. Ax+By=C has slope -A/B because By = -Ax+C y = -A/B x + c/B In this case, A=9 and B=5
*July 12, 2014*

**math**

look at your functions. They indicate that the ball rises as time goes on, and never comes back down. h1(t) = 156 - 16t^2
*July 12, 2014*

**MATH**

IF UNIT IS 1, HOW ABOUT 9871 ?
*July 12, 2014*

**Math**

oops - I plugged in π/2 instead of π. The solution above is correct if the fan is 1/4 of a circle.
*July 12, 2014*

**Math**

The fan is a sector of a circle. That means that 198 = 1/2 (x+3)^2 θ Unless you know how much of a circle the fan occupies (that is, what is θ, compared to 2π), there's no way to solve for x. If the fan is a half-circle, θ=π, so 198 = 1/2 (x+3)^2...
*July 12, 2014*

**English**

They are all four compound sentences, so there should be a comma after "summer" #1 is probably the best. #2 implies that there is a specific group of people under discussion. #3 and #4 suffer from a mismatch between plural and singular.
*July 12, 2014*

**English**

I think #2 is better. The "still" implies that the study is continuing, rather than having been finished in the past. #1 would be ok if it said something like I studied math for ten years, but never really learned it. #1 is still ok as it is, if you are discussing ...
*July 12, 2014*

**English**

The problem appears to be math, and yes, the sentences seem to mean the same thing. Now it's time to work on your English. That would be Do the three mean the same? Or, Are the three the same?
*July 11, 2014*

**Alegbra**

the slopes are the same, so they are either parallel or the same line. If you multiply the 1st by -3, the constant term is different from 7, so the lines are parallel.
*July 11, 2014*

**Surds**

Hmmm. I get √(4x+1)+√(x+3)=2 4x+1 + 2√(4x^2+13x+3) + x+3 = 4 5x = -2√(4x^2+13x+3) 25x^2 = 4(4x^2+13x+3) 25x^2 = 16x^2 + 52x + 12 9x^2 - 52x - 12 = 0 (9x+2)(x-6) = 0 x = -2/9 , 6 But x=6 does not satisfy the original equation, so -2/9 is the only solution.
*July 11, 2014*

**Math**

.075x = 600
*July 11, 2014*

**Math**

it is the square root of 1500. That is, it is the number which, when multiplied by itself, equals 1500. √16 = 4 because 4*4 = 16 √25 = 5 because 5*5 = 25 √1500 is not a rational number, but it is approximately 38.73 38^2 = 1444 39^2 = 1521 So, you can see ...
*July 11, 2014*

**Math**

√1500 so, now what?
*July 11, 2014*

**electric circuit**

are the cells in series or in parallel?
*July 11, 2014*

**math**

13112221
*July 11, 2014*

**trigonometry**

since there's y^2 but no x^2, it's a parabola, opening to the right: 5x = 4y^2 - 3y - 7 x = 4/5 y^2 - 3/5 y - 7/5 x = 4/5 (y^2 - 3/4 y) - 7/5 x = 4/5 (y^2 - 3/4 y + (3/8)^2) - 7/5 - 4/5 * (3/8)^2 x = 4/5 (y - 3/8)^2 - 121/80 so the vertex is at (-121/80,3/8) http://www...
*July 11, 2014*

**math**

what tools do you have at your disposal? Have you learned l'Hospital's Rule yet? If so, that's what I'd use. The limit is the same as for the derivatives: (1/2 cos(x)^-1/2 - 1/3 cos(x)^-2/3)(-sinx) / (1/2 sin(x)^-1/2 * cosx) Take that sinx^-1/2 out of the ...
*July 11, 2014*

**math**

There are many proofs of this, such as the one here: http://www.wyzant.com/resources/lessons/math/calculus/derivative_proofs/sinx However, it relies on the fact that sinx/x -> 1 as x->0. That is usually proven as given here: http://math.ucsd.edu/~wgarner/math20a/sin%28x%...
*July 11, 2014*

**maths**

divide the sum into 5+6+7=18 equal parts of size x. So, 18x = 3600 x = 200 The shares are thus 5*200 = 1000 6*200 = 1200 7*200 = 1400
*July 11, 2014*

**physics**

well you know that AxB = -(BxA) So, if they are equal, they are zero. That means the angle is zero or 180. They are parallel.
*July 11, 2014*

**maths**

look at what we have: a+b+c+d = 66.5 b = a-2 c = a+1.5 d = c+1.5 Start substituting: a+(a-2)+(a+1.5)+((a+1.5)+1.5) = 66.5 a=16.0 b=14.0 c=17.5 d=19.0
*July 11, 2014*

**PHYSICS**

this just algebra I m1*x = m2*3 - m2*x (m1+m2)x = 3m2 x = 3m2/(m1+m2)
*July 11, 2014*

**PHYSICS**

think back to your Algebra I. Collect all the vf terms and factor it out.
*July 11, 2014*

**PHYSICS**

12t + 1/2 at^2 = 25 12 + at = 0 solve for a. Now you can solve for µ by using the resultant acceleration.
*July 11, 2014*

**PHYSICS**

KE = 1/2 mv^2 work is equivalent to energy.
*July 11, 2014*

**PHYSICS**

just a note: that's "mu sub-k," not "muse of k" µk Your class must be an oral presentation, if you never saw it written. Anyway, convert mgh=2.0 * 9.8 * 1.5 to KE, 1/2 * 2.0 * v^2 Using that v, and the frictional force of deceleration, figure the ...
*July 11, 2014*

**PHYSICS**

mgh + 1/2 mv^2 stays constant, so mgh1 + 1/2 m*2^2 = mg(h1-3) + 1/2 mv2^2 divide out all the m's and you have 9.8*h1 + 2 = 9.8(h1-3) + 1/2 v2^2 2 = -9.8*3 + 1/2 v2^2 v2^2 = 62.8 v2 = 7.92
*July 11, 2014*

**PHYSICS**

KE = 1/2 mv^2, so 0.02 = 1/2 * 2 * v^2 ...
*July 11, 2014*

**Phyiscs**

that depends on how long it takes.
*July 11, 2014*

**science**

How many moles of H2SO4 in 10g? The molarity of the final mix is moles H2SO4 / 0.1 L
*July 11, 2014*

**NS 2**

the distance fallen in t seconds is 16t^2. So, when is 16t^2 = 40000? The air speed of 500 mi/hr is irrelevant, since the horizontal speed does not affect the vertical speed.
*July 11, 2014*

**Statistics**

The chance that there are no parents is 10/25 * 9/24 * 8/23 * 7/22 * 6/21 = 6/1265 So, the chance that there is at least one parent is 1259/1265
*July 11, 2014*

**math**

better review what an integer is...
*July 10, 2014*

**College Algebra**

In any case, wolframalpha.com is your friend. It can confirm the results you get through your hard work: http://www.wolframalpha.com/input/?i=%2815x^2-23x-21%29+%2F+%283x-7%29
*July 10, 2014*

**area**

w * 2w = 1000 2w^2 = 1000 w^2 = 500 w = 10√5
*July 10, 2014*

**math**

y = (x-5)(x^2-2x+1) / (x-7)(x^2+2x+3) = (x-5)(x-1)(x-1) / (x-7)(x^2+2x+3) If 5<x<7, the numerator is positive the denominator is negative So, no real value of x between 5 and 7 satisfies the condition that y > 0 That is, unless I have misinterpreted your somewhat ...
*July 10, 2014*

**math**

the discriminant is negative. That means there are no real roots. That means the graph does not cross the x-axis. That means that the value of y never changes sign. so, your job is to justify why that means that y and a have the same sign.
*July 10, 2014*

**Geometry**

tan x = 100/50
*July 10, 2014*

**Geometry**

x/20 = sin 65° the height is the side opposite the 65° angle. sine is opposite/hypotenuse
*July 10, 2014*

**Another question (math)**

while 2 is 67% of 3, that means that 2 is 33% less than 3. 2 is 1 less than 3. 1 is 33% of 3
*July 10, 2014*

**maths**

since the ratio of height to shadow-length is the same, h/22 = 100/55
*July 10, 2014*

**math**

2 log base2 (x+15) - log base2 x = 6 log(x+15)^2 - logx = 6 (x+15)^2/x = 2^6 (x+15)^2 = 64x x^2+30x+225 = 64x x^2-34x+225 = 0
*July 10, 2014*

**math**

4^y = (2^2)^y = (2^y)^2 so, we have a quadratic in 2^y: (2^y)^2 - 7*2^y - 8 = 0 (2^y-8)(2^y+1) = 0 y=3 2^y is never negative, so 2^y+1=0 has no real solution.
*July 10, 2014*

**math**

3 log x = 1 + log (4x+5)/ log 2 That dividing logs stuff is quite unusual for introductory log problems. I will solve 3 log x = 1 + log (4x+5) - log 2 x^3 = 10*(4x+5)/2 2x^3-40x-50 = 0 2(x-5)(x^2+5x+5) = 0 and that's easy If you really did mean to divide the logs, then I ...
*July 10, 2014*

**math**

10^(2x+1) -7(10^x) -26 = 0 10*10^2x - 7*10^x - 26 = 0 10*10^(2*2log t) - 7*10^(2log t) - 26 = 0 10*10^(4log t) - 7*10^(2log t) - 26 = 0 10*(10^(log t))^4 - 7*(10^(log t))^2 - 26 = 0 10t^4 - 7t^2 - 26 = 0 (10t^2+13))(t^2-2) = 0 t = ±√2 or ±√(13/10) i
*July 10, 2014*

**Physics**

If we let +x be eastward, we have <19.98,13.99> or, approximately <20,14> Add that to <0,-10> and the resultant velocity is <20,4> The (eastward) speed with which the boat is crossing the river is 20m/s. Not sure whether I interpreted your language ...
*July 10, 2014*

**math**

-39 + 78 - 100 = -61
*July 10, 2014*

**chemistry**

Ya got me. However, the topic is discussed here: http://en.wikipedia.org/wiki/Magnetic_quantum_number
*July 10, 2014*

**math**

review the significance of the equation (x-h)^2 + (y-k)^2 = r^2
*July 10, 2014*

**trig**

If cosθ = 7/25 in QI, then sinθ = 24/25 That means tanθ = 24/7, and you (ahem) know that tan2θ = 2tanθ/(1-tan^2 θ)
*July 9, 2014*

**math**

35/n
*July 9, 2014*

**math**

you need x ml of solution, and 15-x ml of water (0 mg/ml), so 20x + 0 = 10*15 x = 7.5 Since the concentration is being reduced by a factor of 2, the volume needs to be increased by that factor. 2 * 7.5 = 15
*July 9, 2014*

**math**

If the two heights are h1, and h2 after n hours, the height is h(t) = h1 - (h1-h2)/n t Just plug in all those missing numbers that were not in your post. The burn rate is the height difference divided by how long it took to burn away.
*July 9, 2014*

**math**

The formula is above. Plug in r=3. We will assume a smooth, rather than a dimpled, surface :-)
*July 9, 2014*

**math**

4π(2r)^2 / 4πr^2 = 4 the square of the radius ratio
*July 9, 2014*

**Algebra II**

p? do you mean √? √(b^2+a^2) = √c^2 clearly the next step is flawed. √(b^2+a^2) ≠ b+a while √(b^2*a^2) = √b^2 * √a^2, √(b^2+a^2) ≠ √b^2 + √a^2 I figure you can take it from there
*July 9, 2014*

**Algebra II - Bogus**

I suspect typos. The function is littered with junk. p? +7+8?
*July 9, 2014*

**mathematics**

2x^2-y^2+4x+4y-4=0 2x^2+4x - y^2+4y - 4 = 0 2x^2+4x+2 - y^2+4y-4 -4-2+4 = 0 2(x+1)^2 - (y-2)^2 = 2 (x+1)^2 - (y-2)^2/2 = 1 Now just consult the properties of hyperbolas. x = 2cost y = 3cost First off, I think you have a typo, since that is just 3x=2y If you meant x = 2cost y...
*July 9, 2014*

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