Thursday

October 23, 2014

October 23, 2014

Total # Posts: 26,008

**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*

**Math help!**

(-2)^n+2n: -2+2, 4+4, -8+6, 16+8, ... n^2(-1)^n: -1, +4, -9, ... |10-n^2|: |10-1|, |10-4|, |10-9|, ...
*October 1, 2014*

**Math**

nope - that fixed fee of $32 wrecks the proportion.
*October 1, 2014*

**Math**

the length is clearly 36 cm The pieces can be (36/9)x26 or 36x(26/9) Assuming you want integer dimensions, I'd go with the first choice.
*October 1, 2014*

**Math**

68*3 + x = 70*4 you want large on top and small on bottom, so 984/12
*October 1, 2014*

**Algebra**

what, you have a problem evaluating expressions? (-2)^n+2n: -2+2, 4+4, -8+6, 16+8, ... n^2(-1)^n: -1, +4, -9, ... |10-n^2|: |10-1|, |10-4|, |10-9|, ...
*October 1, 2014*

**algebra2/ trig**

The centers of the pipes form an equilateral triangle, with sides of length 24. The belt then consists of three straight segments of length 24, and three arcs of the circles, subtending angles of 2pi/3.
*October 1, 2014*

**algerbra 1**

Strange language; I suspect you meany "by" 15, so on that basis, we have 2x = 3(x+4)+15 -x = 27 x = -27 and the numbers are -27 -25 -23 check: -54 = -69+15
*October 1, 2014*

**Math**

yes - just divide as shown 7/3 = 2.33 3/4 = 0.75 and so on
*October 1, 2014*

**Math**

#1 ok #2 - the discount was 15%, meaning the actual price was 85%, so 0.85p = p – 150 #3 WHAT? They just told you that A traveled 22 mph faster than B! If car B has speed s, then 2.4(s+22) = 4s This will give you B's speed. The distance traveled was 4s #4 If the ...
*October 1, 2014*

**Math help!**

clearly, at a change rate of -20 per year, (a) -20(5) = -100 (b) -20(-5) = +100 (c) -20n (d) -20(-n) = +20n
*October 1, 2014*

**Trig**

The first plane ends up at (169.7,-169.7) The other plane ends up at (-205.1,-205.1) So, relative to the first, the second plane is at (-374.8,-35.4) arctan(-35.4/-374.8) = 185.4°, or W5.4°S
*October 1, 2014*

**Chemistry/Math**

ppm of what? .01403g is just a mass. That's not much to go on
*October 1, 2014*

**Algebra**

just write each sentence in symbols, then solve the equations. #1 Maria has 105+10m Jana has 0 + 25m So, we want 105+10m = 0 + 25m Now just solve for m and then the amounts #2 There's a rental rate of r, and a late fee of f, so Nate: r + 1f = 5.50 Gina: r + 4f = 10.00 Now ...
*October 1, 2014*

**Math-G7 Help please**

#1 d = b+4 d+b = 22 #5 w(x+y) = 126 y = 2x #8 d+q = 20 10d+25q = 275 #15 s+a = 421 2s+5a = 1244 #17 b = s/3 b+2s = 84 Just translate each sentence into symbols.
*October 1, 2014*

**Math**

4(0) + 1(-3) + 1(-6) + 4x = 63 Now just solve for x
*October 1, 2014*

**math**

change in speed = 8 m/s at 2(m/s)/s, that will take 8/2 = 4 seconds
*October 1, 2014*

**Algerbra math**

(7+2)x^2 + (3+5)x + (9-2) That should help.
*October 1, 2014*

**Math**

any number bigger than the square root of Dalton's area.
*October 1, 2014*

**math**

to find y(x) for a specific x, just replace each x with its value. (a) y(-1) = -3(-1)-2 = 3-2 = 1 and so on (d) -a = -1(a) (e) just solve for x in -3x-2 = -11
*October 1, 2014*

**College algebra**

if there were x reserved seats, then the rest (40000-x) were general admission. So, adding up all the ticket prices, we get 12x + 5(40000-x) = 298000 x = 14000
*October 1, 2014*

**Math- Multi-step word problems**

3(s+20) = 3.20(s-20) s = 620 3*640 = 1920 3840/(3 + 3.20) = 619.35 so you are correct
*October 1, 2014*

**Math- Multi-step word problems**

d/(10-3) = d/(10+3)+1 so you are correct
*October 1, 2014*

**Math- Multi-step word problems**

If the plane's speed is s, then since distance = speed * time, 4(s+10) = 4.15(s-10) That gives s=543.33 553.33*4 = 2213 533.33*4.15 = 2213
*October 1, 2014*

**Math--1 question**

well, you can surely see that 56+c = 83 It's easy to find c, and it's not 33.
*October 1, 2014*

**Trigonometry**

Draw another line making an angle of 28°, passing through the tip of the overhang to the wall. If the height of sunlight on the wall is x, then (20-x)/6.11 = tan 28°
*October 1, 2014*

**math**

that depends on the tools you have at your disposal. Some curves have special properties, like the vertex of the parabola ax^2+bx+c is at x = -b/2a, and so forth. If you have access to calculus, you can find minima on a wider variety of curves. The most general tool would be a...
*October 1, 2014*

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