Friday

February 27, 2015

February 27, 2015

Total # Posts: 29,274

**Calc II**

since the slope anywere is just y'=2x, you want to find where 2x = 5/2 x = 5/4 So, the desired point is (5/4,25/16) For the other one, figure the slope of the tangent line, and then follow the same steps.
*January 29, 2015*

**Calculus**

#1 I only see one point and a number. #2 at the given point, the slope is -1.2 So, the line there is y-0.36 = -1.2(x+0.6)
*January 28, 2015*

**math**

19g/(5cm)^3 = 19/125 g/cm^3 water has density 1g/cm^3, so the wood will float. (duh!)
*January 28, 2015*

**Math**

since cot t appears several places, let g(t) = cot(t) Now we have u(t) = g/(9+g) So, let f(t) = t/(9+t) and you have what you want. f◦g = f(g) = g/(9+g) = cot t/(9+cot t)
*January 28, 2015*

**Math**

If you mean A = 2600e^(0.08t) that is 8% compounded continuously
*January 28, 2015*

**Math**

g(x) = x/(9+x) f(x) = ∛x
*January 28, 2015*

**Math**

f°g°h = f(g(h)) = f(h^2) = √(h^2-5) = √((x^3+6)^2-5) = √(x^6+12x^3+31)
*January 28, 2015*

**Algebra**

get all the T stuff together: 5.5*10^2(1/T) = 17.8 Now you can start working the numbers: 1/T = 17.8/550 T = 550/17.8
*January 28, 2015*

**Math**

If their scores are x and y, we have x/y = 1/5 (x+48)/y = 5/9 Now just solve for y (x+48)/y = x/y + 48/y, so 1/5 + 48/y = 5/9 48/y = 16/45 y = 135 check: x = 27 (27+48)/135 = 75/135 = 5/9
*January 28, 2015*

**Math**

since we have our minimum at t=0, the function will look like y = -cos(kt) The brightness varies by ±0.30, so that is the amplitude. y = -0.30 cos(kt) Since the low is 5.5, the axis of the curve is at 5.5+0.30, so y = 5.80 - 0.30cos(kt) The period of cos(kt) is 2π/...
*January 28, 2015*

**Algebra**

you are correct
*January 28, 2015*

**math**

when x=0, y can be anything, so the points lie on the y axis. It just happens that (0,0) lies on both axes. Now show a counterexample.
*January 28, 2015*

**algebra**

w-9 = m+9 (m-9)/(w+9) = 1/2 Now, solve for w: m=w-18, so (w-18-9)/(w+9) = 1/2 2w-54 = w+9 w = 63 check: m=63-18 = 45 (45-9)/(63+9) = 36/72 = 1/2
*January 28, 2015*

**Trigonometry**

If the point in question is D, then we have AD+DC = 5 BD/AD = tan 60° BD/DC = tan 45° so, we have BD/√3 + BD/1 = 5 Now just solve for BD, the desired distance.
*January 28, 2015*

**Math**

1/5 1/20
*January 28, 2015*

**Math**

1/2 + (2/3)(1/2) = 1/2 + 1/3 = 5/6 That's how much he painted on Mon and Tue. So, that left how much for Wed?
*January 28, 2015*

**Math**

A $1,600.00 principle earns 7% interest, compounded semiannually twice per year. After 33 years, what is the balance in the account. My answer is $112,992.00
*January 28, 2015*

**Algebra 1**

does the rule y=-3x^5 represent an exponential function
*January 28, 2015*

**Calculus**

what does "x^3 x^4" mean?
*January 28, 2015*

**Algebra 1**

Is the following written in scientific notation? 4.8 X 100^7 My answer is no
*January 28, 2015*

**algebra**

just use your formula: 1500(1+0.035)^18
*January 28, 2015*

**Pre-Calc**

using the difference formula, you have sin(x)cos(π/6)+cos(x)sin(π/6) - sin(x)sin(π/6)+cos(x)sin(π/6) = 1/2 2cos(x)sin(π/6) = 1/2 2cos(x)(1/2) = 1/2 cos(x) = 1/2 x = π/3 or 5π/3 http://www.wolframalpha.com/input/?i=sin%28x%2B%28pi%2F6%29%29-...
*January 28, 2015*

**mathematics - eh?**

3/4 - 32 ?? I suspect that your problem is poorly stated.
*January 28, 2015*

**statistics**

1/17259390 times the value of the prize. So, if the prize it at least that much, a $1 ticket expects to make more than a buck.
*January 28, 2015*

**math**

Can't do it. If you draw A,B,C then D can be anywhere on a circle of radius 2.82 with center at C. There are two places on that circle where AD = 7.
*January 28, 2015*

**grammar**

people are there is no preposition here four quarters fell... past tense makes no distinction in number. (except for "to be") it is confusing sometime, all right. A good example is "the number" is singular "a number" is plural
*January 28, 2015*

**mathematics**

since the ratio is constant, 3/4 = x/120
*January 28, 2015*

**Chemistry**

A nice discussion is here: http://www.quora.com/Why-can-chlorine-atoms-not-form-hydrogen-bonds-even-though-they-have-very-similar-electronegativity-to-nitrogen-which-can
*January 28, 2015*

**mathematics**

no idea what a heading (not bearing!) of "1a" is. I also don't see a question in there yet. Nor the distance to point B. In fact, the whole things is garbled. Better clean it up if you expect any meaningful help.
*January 28, 2015*

**10th algebra**

since (x+a)^2 = x2+2a+a^2, you want 2a = 22. So, plug in a=11 and you have c = a^2 = 121
*January 28, 2015*

**MATH**

after x hours, you have the distance d is d^2 = (38x)^2 + (46x)^2 - 2(38x)(46x)cos(135°) so, just solve for x in (38x)^2 + (46x)^2 - 2(38x)(46x)cos(135°) = 214^2 x = 2.75 So, in LA, it is then 12:00 + 2:45 - 2:00 = 12:45 pm
*January 28, 2015*

**Algebra**

all you have to do is sub in the values of f and g: f(x)-g(x) = (-2x+4)-(-6x-7) just add up all the terms and collect like values. What do you get?
*January 28, 2015*

**math**

19 > -n/5 + 9 n/5 > 9-19 n/5 > -10 n > -50
*January 28, 2015*

**Math**

just sub in the value: -a^-2 = -(a^-2) = -1/a^2 = -1/(-5)^2 = -1/25
*January 28, 2015*

**Math**

1/23
*January 28, 2015*

**Math**

well, the point-slope form is y-7 = -4(x+7) now rearrange things into y = mx+b form.
*January 28, 2015*

**math**

#1 subtract 5 from both sides, then multiply through by 9. #2 similarly.
*January 28, 2015*

**maths**

well, since -7 - 1 ≠ 6, that will be hard to do.
*January 28, 2015*

**math**

subtract 15 from both sides, then divide through by -2.
*January 28, 2015*

**Math**

I'll do one, just for grins. if you're taking calculus, you should surely be able to do r = 3+2/(1+0) to get the radius when t=0! Having mastered the arcane art of plugging in a value, and knowing that dr/dt = -2/(1+t)^2 you can probably figure what dr/dt is when t=3.
*January 28, 2015*

**Math 6 grade**

if the percent is greater than 100, that is more than the number. per cent means per 100. 100% is 100 per 100, or all of it.
*January 28, 2015*

**math**

(sinx+cosx)^2 = sin^2 x + 2 sinx cosx + cos^2 x now recall the most fundamental of your trig identities, and the double-angle formulas.
*January 28, 2015*

**physics**

a = F/m
*January 28, 2015*

**physics**

a = v^2/2s = 29.9^2/116.4 = 7.78 m = F/a = 14.5/7.78 = 1.88 to find t, s = 1/2 at^2 clearly the force must act directly opposite its direction of travel.
*January 28, 2015*

**maths**

so, draw your Venn diagram, and start filling in the numbers. Start with the 2 in the center, and then fill in the other numbers so they fit.
*January 28, 2015*

**geometry**

the side of a square with diagonal d is d/√2
*January 28, 2015*

**math**

3/2 x^2 + 10x + 16 = 1/2 (x+4)(3x+8) This is just an exercise in factoring. Now you can easily read off a,b,c
*January 28, 2015*

**math**

4cm is 4 times as big as 1 cm, so you want a distance 4 times as big as 4km.
*January 28, 2015*

**math**

v(x) = (20-2x)^2 * x Of course all real numbers is wrong. The material is only 20 inches square. You cannot include numbers like 500 in the domain. You have to cut two tabs out, so each must be less than 10 in width. 0 <= x <= 10 The base of the box is 20-2x, and must be...
*January 28, 2015*

**Chemistry**

$132/76lb * 13.534g/cm^3 * 16.387cm^3/in^3 * 1lb/453.592g = $0.85/in^3
*January 28, 2015*

**Math. Just checking**

correct
*January 28, 2015*

**Algebra**

it's not always easy. Thus, since you know that #1 adds 5 each time, you expect T(n) = 5n But, T(1) = 5*1=5, not 1, so adjust the starting term: T(1) = 5*1-4 T(n) = 5n-4 or, -4+5n
*January 28, 2015*

**Algebra**

#1 clearly you have to add 5 each time, so T(n+1) = T(n) + 5 explicitly, that means T(n) = -4 + 5n You can do the others similarly.
*January 28, 2015*

**Calculus**

use partial fractions: 1/((x-2)(x+3)(x-4)) = -1/10(x-2) + 1/35(x+3) + 1/14(x-4) Now it's just a bunch of simple logs.
*January 28, 2015*

**Calculus**

you know that d/du tan-1(u) = 1/(1+u^2) So, use the chain rule and you have u = 2x/(1-x^2) du/dx = 2(1+x^2)/(1-x^2)^2 so, the derivative is 1/(1+(2x/(1-x^2))^2) * 2(1+x^2)/(1-x^2)^2 = 2/(1+x^2) to see why this simplifies no neatly, consider that if x = tanθ 2x/(1-x^2) = ...
*January 27, 2015*

**math123**

shift the decimal point till you have a number between 1 and 10: 0.000089956 0.00089956 * 10^-1 0.0089956 * 10^-2 0.089956 * 10^-3 0.89956 * 10^-4 8.9956 * 10^-5 Or, just count the leading zeroes and add 1. Then make that a minus power.
*January 27, 2015*

**Math**

Two obtuse angles cannot both be on the bottom left of the transversal. Anyway, L and M are parallel if the alternate interior angles are equal. or if consecutive interior angles are supplementary. Corresponding angles are usually involved when comparing similar figures. ...
*January 27, 2015*

**math**

That would be 4 * 1 1/4
*January 27, 2015*

**Math**

If x is the foot length, |x-8.5| <= .25
*January 27, 2015*

**Math**

You need both numbers to be multiples of 2. So, use 16:26 42 lbs is the least possible weight.
*January 27, 2015*

**calculus**

not sure what y0...5-4x means anyway, if all you have is two lines, the area is unbounded. If the limits of integration are 0 to 5, and the lines are y = -4x 2x-y-4 = 0 then the lines are y1 = -4x y2 = 2x-4 Now think of the area as a bunch of extremely thin rectangles of width...
*January 27, 2015*

**calculus 1**

the rock hits in √6 seconds. My table is t v (at) 0 0 √6 32√6 avg speed: 32√6/√6 = 32 t s (1/2 at^2) 0 0 √6 96 avg speed: 96/√6 = 16√6 Ya gotta be specific to get what you want.
*January 27, 2015*

**Math**

1/4 is what %?
*January 27, 2015*

**math**

5 + c/9 >= -31 c/9 >= -36 c >= -36*9
*January 27, 2015*

**Calculus II (Math)**

∫ e^u du = e^u u = -.7x du = -.7 dx, so dx = du/-.7 so, ∫5e^(-.7x) dx = 5(1/-.7) e^(-.7x) + C
*January 27, 2015*

**Too bad**

you can't just come rushing in here and drop a 23-problem homework assignment and expect someone to rush up and do all your work for you. Lack of preparation on your part does not constitute a crisis for me.
*January 27, 2015*

**Algebra 2**

since 10^3 = 1000, 10 = 1000^(1/3) 1/10 = 1000^(-1/3) so, your log_1000(0.1) = -1/3 1000^x = 0.1 works just fine; you just have to know how to evaluate it. x = -1/3
*January 27, 2015*

**Math**

time = distance/speed, so 725/(390-65)
*January 27, 2015*

**Algebra**

(23-20)/23 * 100
*January 27, 2015*

**Math**

6-4b <= 14 -4b <= 8 b >= -2
*January 27, 2015*

**math**

the discriminant is 25 - 8k so, for one (repeated) root, 25-8k=0 find that, and then any value of k greater will produce a negative discriminant any lesser value of k will produce a positive discriminant.
*January 27, 2015*

**arithmetic**

(a) a+9d = 31 a+14d = 49 d = 18/5 a = -7/5 so, we have -7/5, 11/5, 29/5, ... (b) and (c) are just the same. (d) a+8d = a+16x = 7+9x a = 7-7x so, 7-7x, 7-5x, 7-3x ...
*January 27, 2015*

**ALGEBRA**

can't. text only at this site.
*January 27, 2015*

**matha**

70 + x + (x-20) = 180 Now you can find x, and figure the other two angles.
*January 27, 2015*

**MATH!!**

if the difference is constant, it's arithmetic. If the ratio is constant, it's geometric. #1 is clearly arithmetic #2 is geometric #3 is too #4 15 + 1.5 + 1.5 ... #5 4.5 * 10 * 10 ...
*January 27, 2015*

**science**

well, what does a fan do when you turn it on?
*January 27, 2015*

**algebra**

Never heard of it. What does the question really say?
*January 27, 2015*

**Physics**

I'm having a hard time making out the figure. . .
*January 27, 2015*

**science**

the circumference of the frame is πd m The total length of wire is 5*50 = 250 m So, ignoring the slight difference of the length of a helix as opposed to stacked rings, the number of loops around the frame is 250/πd The height of each loop is 0.035 m, so (250/πd...
*January 27, 2015*

**algebra**

-49x^2-35x-6 -(49x^2+35x+6) -(7x+2)(7x+3)
*January 27, 2015*

**Math**

clearly, 12 does not divide either polynomial. 4x^2 + 13x + 3 = (4x+1)(x+3) 8x^2 + 22x - 6 = (4x-1)(x+3) Now can you see the common factor? How ever did you come up with 12?
*January 27, 2015*

**BOGUS!**

expect no help till you finish the question. Do you see what you actually wrote? No diagram, no description of what D and E are. BOGUS!
*January 27, 2015*

**math**

well, (2+4+6+...+200) = 2(1+2+3+...+100) 1+2+3+...n = n(n+1)/2 So, x = 200*201/2 and you have 200*201/2 - 2*100*101/2 = 200/2 (201-101) = 100*100 = 10,000 Or, you could note that (1+2+3+...+200)-(2+4+6+...+200) = (1+3+5+...+199) The sum of the first n odd numbers is n^2, so ...
*January 27, 2015*

**math**

divide each price by its area. The smallest quotient is the best buy in $/m^2. How you factor in the quality is not specified.
*January 27, 2015*

**math**

a+b = 12 1/a + 1/b = 3/8 4+8 = 12
*January 27, 2015*

**math**

I expect you meant to say (2,-√5) man, some of the weird notations folks come up with! The line passing through the origin with slope m is y = mx You have a point, so you can figure the slope, right? The tangent line to a circle at any point (x,y) is -x/y SO, you want to...
*January 27, 2015*

**math**

answered in the first related question below.
*January 27, 2015*

**MATH**

75(b-4) <= 450
*January 26, 2015*

**Math**

no grids here, but surely you can see that the dimensions must be among 1x7 2x6 3x5 4x4
*January 26, 2015*

**Physics - Vectors**

when you say A times B, is that the dot product, or the cross product?
*January 26, 2015*

**Physics - Vectors**

not sure what Upper B means
*January 26, 2015*

**Physics**

conserve momentum. So, 2.33*10^4 * 3.71 + 4.66*10^4 * 1.44 = 6.99*10^4 * v v = 2.20 m/s So, now just figure KE = 1/2 mv^2 for each car before, and the combo car after the collision.
*January 26, 2015*

**Geometry**

there are lots of possible probabilities. For each color, P(color) = #color/#total so P(red) = 5/(4+5+1+2) = 5/12 do the others similarly.
*January 26, 2015*

**Algebra**

2(w + w-1) = 106 4w-2 = 106 4w = 108 w = 27 so, the width is 27 and the length is 26. An odd way to assign the dimensions, I must say... You forgot that the perimeter is twice the sum of the length and width.
*January 26, 2015*

**Math**

r = s+6 in 4 years, r+4 + s+4 = 78 so, now we can see that (s+6)+4 + s+4 = 78 2s+14 = 78 2s = 64 s = 32 SO, Samantha is 32 and Russell is 38 In 4 years, they will be 36 and 42 (sum = 78)
*January 26, 2015*

**MATHS**

in 2 hours, they can fill 2(1/10 + 1/8) = 9/20 of the pool. So, at 1/10 pool/hr, A takes an additional (11/20) / (1/10) = 11/2 hours
*January 26, 2015*

**Math**

I understand the question to mean that the difference in attendance was at least 16,600, so I'd write it as x-809,300 >= 16,700 x >= 826,000 Note that "at least" means greater or equal, not just greater.
*January 26, 2015*

**Math**

how many times you gonna ignore Reiny's explanation below, or at least say why it is unsatisfactory?
*January 26, 2015*

**Geometry**

I suspect it makes a difference which direction each one turns.
*January 26, 2015*

**Math**

the period of cot(x) is pi. The amplitude and power make no difference. So, the general solutions are n*pi ± pi/3 for any integer n.
*January 26, 2015*

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