Monday

October 20, 2014

October 20, 2014

Total # Posts: 25,933

**Calculus**

well, if y = sin^2(u) y' = 2 sinu cosu u' u' = ln3 3^x y' = 2ln3 3^x sin(3^x) cos(3^x) = ln3 3^x sin(2*3^x) I think you got some of your 3's mixed up as powers of sin. You appear to have taken the derivative of sin^3 (3^x)
*October 5, 2014*

**Algebra 2 (Please, help me!)**

Take |x| shrink it horizontally by a factor of 2: |2x| shift it down 3: |2x|-3 Now shrink it vertically by a factor of 4: (|2x|-3)/4 http://www.wolframalpha.com/input/?i=plot+y%3D|x|%2C+y%3D%28|2x|-3%29%2F4
*October 4, 2014*

**Math**

Since the border is on both sides, 5 + 2(2 1/4) = 9.5 7 + 2(2 1/4) = 11.5 2(9.5+11.5) = 42
*October 4, 2014*

**Math**

X^2+4x=10 x^2+4x+4 = 10+4 (x+2)^2 = 14 x+2 = ±√14 x = -2±√14
*October 4, 2014*

**Math**

that will of course be x miles where 100+.60x = 50+.80x
*October 4, 2014*

**algebra**

How could a quadratic be anything like a linear function?
*October 4, 2014*

**algebra**

You could think of it as a shifted parabola, where 2x+3(x-2)^2 = 3(x-2)^2 + 2(x-2) + 4
*October 4, 2014*

**algebra**

Is there a question in there somewhere?
*October 4, 2014*

**Calculus**

the indicated line has slope -1. y' = 6x+4 6x+4 = -1 when x = -5/6 y(-5/6) = -5/4 So, the line is y = -(x+5/6) - 5/4 http://www.wolframalpha.com/input/?i=plot+y%3D3x^2%2B4x%2C+y+%3D+-%28x%2B5%2F6%29+-+5%2F4
*October 4, 2014*

**Physics**

How long does it take to drop 785m? 4.9t^2 = 785 Then the horizontal distance traveled in that time is 53.5t
*October 4, 2014*

**Algebra**

z- 1/5 > 1/4 My answer is z < 9/20
*October 4, 2014*

**Physics**

think on it. If the angle of elevation is 0, a = 0 if x = 90 degrees, a = g So, what trig function has its zero at x=0, and its max at x = 90 degrees?
*October 4, 2014*

**Algebra**

If m play in marching band, then m+250-130 = 375 m = 255 How did you arrive at 135? I can see 125, but not 135. Anyway, the question was not "how many play only in the marching band?"
*October 4, 2014*

**math**

Let x be the number of 10-person increases. So, since revenue is price*people, R(x) = (200+10x)(30-1.50x) That is just a parabola, with its vertex midway between the roots, at x = (-20+20)/2 = 0 That is, max revenue for just 200 people. That is assuming that the price decrease...
*October 4, 2014*

**Algebra**

3*85 <= 83+91+x <= 3*90 255 <= 174+x <= 270 81 <= x <= 96
*October 4, 2014*

**Algebra**

correct. But I suspect that was not really the question. If the question was asking for P', then that would be {2,4,6,8} When talking about sets, it's better to use the braces; otherwise, you just have a list, not a set.
*October 4, 2014*

**Algebra**

Hmmm. You think 5 is a factor of 16? If so, you need to review the term "factor". Better prune your list a bit.
*October 4, 2014*

**AP Statistics**

From the Z table, the 10% tail is 1.282 std from the mean. Since the 10% tail is used on both ends, the mean is halfway between where the tails start. That help?
*October 4, 2014*

**algebra**

x=1, y=2: x+y=3, 3x+2y=9 (8)(9)(x+y)/(3x+2y) = 24
*October 4, 2014*

**Science**

correct again.
*October 3, 2014*

**Physics**

Oops -- v = -9.8t
*October 3, 2014*

**Physics**

horizontal speed is constant: 30.9/3.03 m/s The vertical speed is v = at = -4.9t The angle x is such that tan(x) = Vy/Vx
*October 3, 2014*

**Physics**

the height is h(t) = 20.7t - 4.9t^2 That's just a parabola; the max height is at the vertex. Now just solve for t when h=0. To save yourself some work, the max height is reached at the center of its flight, so you really only need to calculate one of the above answers, ...
*October 3, 2014*

**Science**

You are correct.
*October 3, 2014*

**math**

6^2 = 36 1+3+5+7+9 = 25 + 4 = 29 2^5 = 32
*October 3, 2014*

**math**

200 * 0.1 = ? Ever hear of a calculator?
*October 3, 2014*

**Math**

True, but we also have (a+9)(a+16) = a^2 + 25a + 144
*October 3, 2014*

**one last difference (math)**

I think you need to reword your question. 1.2 is the fraction less than 1.8 Now, if you want to know how much less than 1.8 1.2 is, then of course that would be 1.8-1.2 = 0.6
*October 3, 2014*

**math**

So, did you use the table?
*October 3, 2014*

**math 156**

P(1+.04/4)^(4*6) = 35000 Now just solve for P.
*October 3, 2014*

**math**

Just match the values in pairs. A. Each pair adds up to 1002 B. Each pair adds up to 100 Now just figure out how many pairs there are.
*October 3, 2014*

**algebra 2**

x=9 2x+3y = 30 Now the rest of the questions get easier.
*October 3, 2014*

**pre-calc**

Clearly, since we have a semicircle, the width of the rectangle is half the length. So, A = (3x/2)(3x) P = 2(3x/2 + 3x)
*October 3, 2014*

**Physics**

If you are not familiar with the equations for trajectories, the wikipedia article for that subject has a good treatment. Just plug in your values for the equation of motion, and crank it out. If you get stuck, come on back with your work so far, and we can give you a nudge in...
*October 3, 2014*

**Math**

In that case, review your basic trig functions. cos(x) = 7/21 Now just find x, with that value for cosine.
*October 3, 2014*

**Pre-Calc/Trig...**

No idea. But the answer is clearly B, if for no other reason than that x and y have opposite signs on the left.
*October 3, 2014*

**Pre-Calc/Trig...**

recall the point-slope form of a line. In this case, y-1 = 3(x-10) Now massage that into one of the choices.
*October 3, 2014*

**houston community college**

Since PV=kT, PV/T is constant. So, since P is constant, V/T is constant. That means: 1.4/(27+271) = V/(177+271)
*October 3, 2014*

**Calc**

I don't know what the original problem was, but if the doubling time is 24 days, the formula for the amount present after t days is A(t) = Ao * 2^(t/24) Since 2 = e^ln2, that is equivalent to A(t) = Ao * e^(ln2/24 t)
*October 3, 2014*

**AP CALC. AB**

f(x) = 3/x f'(x) = -3/x^2 So, we want -3/c^2 = 3(-3/4) c^2 = 4/3 ...
*October 3, 2014*

**calc**

when t=0, Q=0.414 = a e^.885 = 2.423, so Q = .414(2.423^t) population grows by a factor of 2.423 every period. well, duh: k = 0.885 = 88.5%, though it's not usually expressed as a percent. Actually, that's k if you express Q as a e^kt
*October 3, 2014*

**trig**

sin(x) = 12/15, so ...
*October 3, 2014*

**Pre-Calculous**

.887 = e^-.1199, so .887^1.2t = e^(-.1199*1.2t) = e^-.144t It's always better to show your work, so we can help correct the errors, if any.
*October 3, 2014*

**AP Calc. AB**

when the tangent passes through the origin, it is of the form y = kx So, we want places where the slope is y/x. y' = 20x^4 - 12x^3 + 30x So, we want places where 20x^4 - 12x^3 + 30x = (4x^5-3x^4+15x^2+6)/x That is, where 20x^5-12x^4+30x^2 = 4x^5-3x^4+15x^2+6 16x^5-9x^4+15x...
*October 3, 2014*

**CALCULUS**

you want 1.043^t = 2.0 t log 1.043 = log 2 t = log2/log1.043 = 16.5 years This is roughly in accordance with the rule of 72: 72/4.3 = 16.7
*October 3, 2014*

**Math**

since cot(z) has asymptotes at all multiples of pi, h(x) above will have asymptotes at all places where x/2 is a multiple of pi.
*October 3, 2014*

**Physics**

Two satellites, A and B, are in different circular orbits about the earth. The orbital speed of satellite A is eighty-two times that of satellite B. Find the ratio (TA/TB) of the periods of the satellites.
*October 3, 2014*

**English**

yes and yes
*October 3, 2014*

**math**

The size of the cut will not, of course, change the length of the board. It will, of course, affect the total length of the cut pieces, since 1.25" will be lost after 10 cuts. I suspect there is more to this problem than what you asked, but if you want answers, you have ...
*October 3, 2014*

**geometry**

That would be 672 - (-36) = ?
*October 3, 2014*

**math**

If $x go at 2%, the rest (4000-x) is at 5%. So, add up the interest on each part: .02x + .05(4000-x) = 155.00
*October 3, 2014*

**algebra**

If the plane's speed is p, and the wind's speed is w, then since distance = speed * time, 3(p+w) = 1500 3(p-w) = 1380 Now you can easily find p, and then w.
*October 3, 2014*

**Math**

yes.
*October 3, 2014*

**physics**

total distance: 15.9+25.3+34.3 = 75.5 mi total time: 15.9/51 + 25.3/41 + 34.3/38.6 = 1.82 hr So, avg speed is 75.5mi/1.82hr = 41.55 mi/hr
*October 3, 2014*

**Math**

no - that fixed fee of $32 wrecks the proportion.
*October 3, 2014*

**Math**

First, the income in 2010 is not P(10), it is P(3). P(t) is only defined for 2<t<6, where t is the years since 2007. P(3) = 6(3)-24 = -6, so P(t) is decreasing there. Note that P'(t)=0 when t=4. That means it is decreasing more slowly until t=4, then starts to ...
*October 2, 2014*

**Calculus**

You have the right idea, but y' = 1 - 1/(2√x) Setting that to zero, we get 1 - 1/(2√x) = 0 1/(2√x) = 1 2√x = 1 √x = 1/2 x = 1/4 As you can see from the graph, there is only the one point (1/4,-1/4) with a horizontal tangent. http://www....
*October 2, 2014*

**Math**

Do you know what the midpoint is? It is the point midway between A and C. That is, it is the same distance from A as it is from C. That is, AB = BC
*October 2, 2014*

**Calc**

both wrong. Better review the definition of continuous. sin(x)/x -> 1 as a limit as x->0, but 0/0 is not defined, so it is not continuous there.
*October 2, 2014*

**Math**

p = (74.5+124.2)/242 p is not 1.0, because of things called divorce and death.
*October 2, 2014*

**physics**

since the distance s = vt + 1/2 at^2, 4780*525 + 525^2/2 ax = 3.54*10^6 8850*525 + 525^2/2 ay = 7.77*10^6
*October 2, 2014*

**math**

For F(x,y) = 3y cosx, we have Fx = -3y sinx Fy = 3 cosx Fxx = -3y cosx Fyy = 0 Fxy = -3 sinx So, for a saddle point, we need Fx = 0 true for x=0,pi or y=0 Fy = 0 true for x=pi/2, 3pi/2 and all y Fxx * Fyy - (Fxy)^2 < 0 -3y cosx * 0 - (-3 sinx)^2 < 0 true for all x. The ...
*October 2, 2014*

**pre calculus**

since d/F is constant, .15/265 = .2/x and, .165/265 = x/100 Note that you don't really have to find k, the constant of proportionality. You can go ahead and find it, but your answers will be the same.
*October 2, 2014*

**math**

approximate: use 30 days per month. exact: get a calendar.
*October 2, 2014*

**Math**

At x=2, x-5 < 0, so the slope at x=2 is just -1. Ok, ok, algebraically, f(2+h) = |2+h-5|-7 = |-3+h|-7 Since the value is negative, that will be 3-h-7 = -4-h f(2) = |2-5|-7 = 3-7 = -4 -4-h - (-4) = -h Now, divide by h and you have -h/h = -1
*October 2, 2014*

**Math**

pretty good, but you know that cot π/4 = 1 csc π/4 = √2, so m = -12(1)(2) = -24 So the line is y-3 = -24(x-π/4)
*October 2, 2014*

**geometry**

If the points are in a aline, then I expect AB + BC = Ac So, 9a + 12a = 42 21a = 42 a = 2 Now you can figure out the lengths AB and BC
*October 2, 2014*

**Math (Implicit Differention)**

of course, you can simplify that last result to just √3, since it is (3^(3/2))^(1/3) = 3^(1/2) Also, you dropped/gained a minus sign in there somewhere. The point is in QII, where the slope is positive.
*October 2, 2014*

**calculus**

x^2/3+y^2/3=4 2/3 x^-1/3 + 2/3 y^-1/3 y' = 0 y' = -(y/x)^1/3 So, at (-1,3√3), y' = -(3√3/-1)^(1/3) = √3 You can see the graphs at http://www.wolframalpha.com/input/?i=plot++x^%282%2F3%29%2By^%282%2F3%29%3D4+%2C+y+%3D+-%E2%88%9A3%28x-1%29+%2B+3%E2%...
*October 2, 2014*

**Math - Please Check My Answer - Probably Last One!**

the ratio is just (πr^2h) / (2r)^2*h πr^2h / 4r^2h π/4
*October 2, 2014*

**Math - Please Check My Answer**

D is correct. In A, 3x^0 = 3*1 = 3, while (3x)^0 = 1 (assuming x is not zero)
*October 2, 2014*

**AC DC Circuit fundamentals**

since they are in series, the voltage drop is divided up into 2/3 across the 10k 1/3 across the 5k since R = R1+R2 = 5+10 = 15 k, and 10 is 2/3 of 15, 5 is 1/3 of 15.
*October 2, 2014*

**Trigonometry**

f(x-a) is f(x) shifted right by a. So, yours is shifted left by 5. f(x)+k is f(k) shifted up by k.
*October 2, 2014*

**Math**

4(x+15) >= 120 x+15 >= 30 x >= 15
*October 2, 2014*

**Math**

3/2 + 23 since max of sine is 1.
*October 2, 2014*

**Math**

right again.
*October 2, 2014*

**Math**

both correct!
*October 2, 2014*

**Trigonometry**

since the maximum of sin(x) is 1, d(t) achieves a maximum of 3/2 + 23.
*October 2, 2014*

**Math**

Just do hex long division, as at http://mathforum.org/library/drmath/view/63375.html However, it is sometimes easier to convert to decimal, divide, and convert back.
*October 2, 2014*

**Algebra ll**

division by zero is not defined. What is 12/0? 0/0? So, for a rational function, the domain excludes any values where the denominator is zero, because the domain is the set of values of x for which f(x) is defined. For f(x) = (x^2 - 25)/2 the domain is all real numbers; there ...
*October 2, 2014*

**Simplify this Expression?**

You can do it using the distributive property as J and Ms Sue did, or you can use it implicitly, working term by term z-2z+4z+6 -z+4z+6 3z+6 Their answers basically factored out the z, as in z-2z+4z+6 (1-2+4)z+6 (3)z+6 3z+6
*October 2, 2014*

**geometry**

think of alternate interior angles, or consecutive interior angles.
*October 2, 2014*

**Trigonometry**

Just do things as you normally would. tan 28 = 0.5317, so you have (20-x)/6.11 = 0.5317 20-x = 3.25 x = 16.75 Don't forget your algebra I just because you're taking trig now!
*October 2, 2014*

**math**

Looks to me like .013
*October 2, 2014*

**Plane and Spherical Trigonometry**

Use the law of cosines. The third side can be found using AC^2 = 20^2 + 35^2 - 2(20)(35)cos(180-80)°
*October 2, 2014*

**math**

(g-48)(g-20) = 480 g = 60 So, the grandfather is 60. ...
*October 2, 2014*

**Math**

1/4 * 1/2 = 1/8
*October 2, 2014*

**math**

(14 - (15/3))/2 = 9/2
*October 2, 2014*

**English - Parts of Speech**

a simple google search will provide numerous examples.
*October 2, 2014*

**maths**

sorry, no diagrams here. But I bet you can do it. Just look in your text (or online) for similar situations, and change the numbers. You just have to draw two intersecting circles.
*October 2, 2014*

**algebra**

7 + 2x
*October 2, 2014*

**Physics**

A 0.60-kg basketball is dropped out of the window that is 6.1 m above the ground. The ball is caught by a person whose hands are 1.2 m above the ground. (a) How much work is done on the ball by its weight? (b) What is the gravitational potential energy of the basketball, ...
*October 2, 2014*

**Physics**

The drawing shows two boxes resting on frictionless ramps. One box is relatively light and sits on a steep ramp. The other box is heavier and rests on a ramp that is less steep. The boxes are released from rest at A and allowed to slide down the ramps. The two boxes have ...
*October 2, 2014*

**Math**

as with all fractions, multiply top and bottom by the GCD (a-1)(b) to get 1/(a-1) + 1/b = c b + (a-1) = c(a-1)(b) b + a - 1 = abc - bc a - abc = 1 - b - bc a = (1-b-bc)/(1-bc) = 1 + b/(bc-1)
*October 1, 2014*

**Precalculus**

If the width surrounding the rug is w, then (12-2w)(16-2w) = 12*16/2 Now just solve for w and determine the rug dimensions.
*October 1, 2014*

**calculus**

The curves intersect at (4,0) and (1,3). You don't specify the axis, so, assuming the x-axis, using shells, the volume is v = ∫[0,3] 2πrh dy where r = y and h = (5-(y-1)^2)-(4-y) v = 2π∫[0,3] 3y^2 - y^3 dy = 27π/2 Using washers, we have to break ...
*October 1, 2014*

**Algebra HELP!**

No ideas on any of them? Look for groupings of like expressions, difference of two squares, etc. For example, (g) is (x^2-y^2) + x + y (x-y)(x+y) + (x+y) (x-y+1)(x+y)
*October 1, 2014*

**Algebra**

Looks good to me. I tend to avoid fractions where possible, so I'd probably have done it as 42+48+x = 3*47
*October 1, 2014*

**Math**

(6+2w)(12+2w) = 520 w = 7
*October 1, 2014*

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