Sunday

December 21, 2014

December 21, 2014

Total # Posts: 27,653

**Algebra help**

ok ok v = 243 - 0.2s
*November 6, 2014*

**Physics**

Consider m3 to be at (0,0) m1 exerts its force at an angle of 30° m2 exerts its force at an angle of -30° As you say, each force is F=GMm/r^2 The resultant force will be at 0°, with a magnitude of F√3, the sum of the x-components of the two forces.
*November 6, 2014*

**Calculus**

y = (3x^2+2√x)/x = 3x + 2/√x y' = 3 - 1/x^3/2 You are correct
*November 6, 2014*

**Trigonometry**

secx = 2.1754 x = 0.4776 SInce secx is positive in QI and QIV, the other angle is 2π-0.4776 arcsin(2x) makes no sense, since x is an angle. That's if we are still referring to the first question. Now, in general, if sinθ = 2x, then cosθ = √(1-sin^2&#...
*November 6, 2014*

**Trigonometry**

c = 2πr, so one revolution of the plane travels 4π meters So, now we know that 5 min * 60s/min * 0.4rev/s * 4πm/rev = (5*60*4π)/(0.4) = 300π meters
*November 6, 2014*

**Math**

There is a good discussion of this problem at http://mathforum.org/library/drmath/view/65003.html This is, of course, a case involving Fermat's Last Theorem.
*November 6, 2014*

**Math- Had Sub teacher, need help**

apparently you stopped reading before finishing things. Read on past where it says So, the revenue will be ...
*November 6, 2014*

**Math- Had Sub teacher, need help**

revenue = rent * apts if there are x $7 increases, then we have rent = 294+7x units rented = 120-x So, the revenue will be (294+7x)(120-x) = -7x^2 + 546x + 35280 Recall that the vertex of a parabola is at x = -b/2a, which in this case is x = 546/14 = 39 So, with 39 rent ...
*November 6, 2014*

**Algebra**

recall that the vertex of a parabola is at x = -b/2a, which in this case is x = 1/.0064 = 156.25 so, just find f(156.25)
*November 6, 2014*

**Math - incomplete**

better explain some more about the diagram.
*November 6, 2014*

**Math help!**

m=r+4 m-10 = 3(r-10) Miriam is 16 and Ricardo is 12
*November 6, 2014*

**Calculus**

in that case, z^2 = (x+3)^2 + (5(x+3)/x)^2 z = (x+3)√(x^2+25) / x dz/dx = (x^3-75) / x^2√(x^2+25) and x = ∛75
*November 6, 2014*

**Calculus**

If the foot of the ladder is x feet from the fence, and it reaches to a height h on the wall, then using similar triangles, x/3 = (x+7)/h h = 3(x+7)/x the ladder's length z is z^2 = (x+7)^2 + h^2 = (x+7)^2 + (3(x+7)/x)^2 z = (x+7)√(x^2+9) / x So, for minimum z, we ...
*November 6, 2014*

**CAL**

#1 correct #2 is only partially complete f'(x) or df/dx y' or dy/dx
*November 6, 2014*

**CAL**

The _____________ of a function is a formula for the slope of the tangent line to that function at any point x. When the function is defined as f(x), the derivative will be written as __________or ________. When the function is written in the form of y =, the derivative is ...
*November 6, 2014*

**Calculus**

ohhh.. I think I know what I did wrong.. I did not even realize that I was doing something completely different
*November 6, 2014*

**Calculus**

wow - remember the chain rule if u = cos(x^4) then we have y = u^4 y' = 4u^3 u' y' = 4 cos^3(x^4) * (-sin(x^4)(4x^3) = -16x^3 sin(x^4) cos^3(x^4) y = sinx/(1+cos^2(x)) y' = [(cosx)(1+cos^2(x)) - (sinx)(2cosx)(-sinx)]/(1+cos^2(x))^2 y = sinx(sinx+cosx) y' = ...
*November 6, 2014*

**Calculus**

Find the derivatives of the following 18. y=〖cos〗^4 x^4 ANSWER: tanx2 19. y= sinx/(1+ 〖cos〗^2 x) ANSWER: 3sinx 20. y=sinx(sinx+cosx) ANSWER: sinx Can you check my answers?
*November 6, 2014*

**Math Help**

since loga + logb = log(ab) we have 4(ln(z(z+5)) = ln (z(z+5))^4 2ln(z-5) = ln (z-5)^2 Now, since loga - logb = log(a/b), we have ln ( (z(z+5))^4 / (z-5)^2 )
*November 6, 2014*

**Calculus**

Looks good to me. Nice work.
*November 6, 2014*

**Calculus**

3G 4H 5F 6B (though I never heard of such a term) 7E 8C 9A 10D Wow - either your order is mixed up, or you have some serious reviewing to do...
*November 6, 2014*

**Calculus URGENT**

f(x) = √x f(0) = 0 f(9) = 3 So, the slope of the secant is 1/3 f'(x) = 1 / 2√x So, we want to find c such that 1 / 2√c = 1/3 √c = 3/2 c = 9/4 So, c is in the interval [0,9] just to check, f(9/4) = 3/2 So, the equation of the tangent line at c is y...
*November 6, 2014*

**Algebra 2**

192x^2y + 72x^3 = 24x^2(8y+3x) 24rxy - 9rx^2 = 3rx(8y-3x) The only common factor I can see is 3x, so we have 3x(64xy+24x^2-8ry+3rx) Not sure just where you're trying to go with this Now, if the original had been without the parentheses, (192x^2y+72x^3)-24rxy-9rx^2 then we ...
*November 6, 2014*

**matg**

20 years is 4 half-lives, so there would be 300 * (1/2)^4
*November 6, 2014*

**Science**

PE = mgh = (45)(9.81)(2) J
*November 6, 2014*

**Math**

I get z(2.75,0) = 22
*November 6, 2014*

**physics**

recall your equation of motion. In this case, the height, as a function of t is h(t) = 2.54t - 4.9t^2 This is just a parabola, with the vertex at t = -b/2a = 2.54/9.8 = 0.26 So, just plug in t=0.26 to find the maximum height, h(0.26)
*November 6, 2014*

**algebra**

It's easy to construct such a polynomial with zeroes that are very difficult to find: 3x^5 - 12x^4 + 9x^3 + x^2 - 12 But, if you start out with the roots, it's easy to build the polynomial: (x-3)(2x+5)(3x-7)(x^2+4) = 6x^5 - 17x^4 - 14x^3 + 37x^2 - 152x + 420
*November 6, 2014*

**geometry**

draw a line mark point A. mark point B at a distance of 8.5 units away from A. Now, draw a circle of radius 6.2, with center at B. Point C can be anywhere on the circle just drawn.
*November 6, 2014*

**Math**

.815 = 815/1000 .021 = 21/1000 So, she added thusly: 5 815/1000 + 6 21/1000 = 11 876/1000 = 11 219/250
*November 6, 2014*

**math**

1.2 - (0.75 + 0.125 + 0.09) = 1.2 - 0.965 = 0.235
*November 6, 2014*

**math**

recall the slope-intercept form of a line: y = mx+b
*November 6, 2014*

**Object Oriented Programming Concept Using C++**

use how? R = 2T?
*November 6, 2014*

**Math**

y = x^2+6x+4 = x^2+6x+9 + 4-9 = (x+3)^2 - 5
*November 6, 2014*

**math**

For x motors, $150, so each cost 150/x For a cost of 150/x - 5, then there were x+1 motors, all for the same $150: (x+1)(150/x - 5) = 150 x = 5 check: 5 @ $30 = 150 6 @ $25 = 150
*November 6, 2014*

**math**

(5+x)/(6+2x) = 3/5
*November 6, 2014*

**math**

original price for x radios is 1200/x So, (x-6)(1200/x + 10) = 1200
*November 6, 2014*

**math**

look at the multiples of 4 0 4 8 12 16 20 ... You can also consider that since the second number is 1 times the row number, then the row is 4.
*November 5, 2014*

**algebra help please**

well, just plug in the value for t: t=5: 2200 + (-480*5) = 2200-2400 = -200 and do the others the same way
*November 5, 2014*

**please help! algebra**

clearly there is no constant difference. Check for constant ratio (-12)(-5) = 60 (60)(-5) = -300 ... we have a winner. SO, what is 1500 * -5 ?
*November 5, 2014*

**Trig**

well, if you insist on using tan, then note that the base of the slide is √(250^2 - 107^2) = 225.9 cm out from spot directly under the slide's top. So, now we have tan θ = 107/225.9 = 0.47 θ = 25.3°
*November 5, 2014*

**Math, please help**

subtract the area of the painting from the total area. If the matte has width w, then (10+2w)(15+2w) - 10*15 = 10*15 4w^2 + 50w - 150 = 0 2(2w-5)(w+15) = 0 w = 5/2 = 2.5
*November 5, 2014*

**Math**

no way to tell the perimeter from just the area. All we know is that the smaller dimension is greater than 1.7 m.
*November 5, 2014*

**Help please Math**

No, what you want is a(bc) = (ab)c multiplication is associative. It is also distributive over addition: a(b+c) = ab + ac Of course, if a=1, a(bc) = (ab)(ac) because 1(bc) = (1a)(1b) = bc
*November 5, 2014*

**pre-algebra**

Nope. It triples every 4 hours, so in 24 hours it has tripled 6 times: x * 3*3*3*3*3*3 = x * 3^6
*November 5, 2014*

**chemistry**

since PV=kT, PV/T is a constant. So, using the given numbers, (.14 atm)V/(271+48) = (756 torr)(.295)/(271+18) You will need to reconcile atm and torr, and then solve for the new V
*November 5, 2014*

**Algebra**

not much of a scenario. They want a situation in real life which would produce such a decline and then increase in typing speed.
*November 5, 2014*

**geometry - incomplete**

how is point G defined?
*November 5, 2014*

**TRIG WORD PROBLEMS**

not sure just what you did, but if the height is x, then x/25 = tan 38° Actually, x is the shorter leg. The 38° angle is from the ground to the top of the building.
*November 4, 2014*

**Calculus- Please Help!**

Since moles is constant, nR is constant. SO, V dP/dt + P dV/dt = nR dT/dt You now have n = 2*6.02*10^23 P = 5 V = 15 dP/dt = -3 dV/dt = 0.6 So, plug in the numbers and solve for dT/dt
*November 4, 2014*

**English**

Thank you
*November 4, 2014*

**English**

In the Call of the Wild, Buck did not fight back when Hal was beating, him because? My answer is that he did not have the strengh
*November 4, 2014*

**English**

Thsnk you very much.
*November 4, 2014*

**English**

The hairy man represents what in the call of the wild? My answer is fear
*November 4, 2014*

**calculus**

v = ds/dt = 2/√(1+4t) a = dv/dt = -4/(1+4t)3/2 now just plug in t=6
*November 4, 2014*

**physics-distance**

r dθdt = .5 * 6.9 = 3.45 m/s is the linear speed. so, 3.45 m/s * 35*60 s = 7245 m
*November 4, 2014*

**Algebra 2**

(5+2w)(12+2w) - 5*12 = 168 Now just solve for w.
*November 4, 2014*

**Algebra**

that would be the plan. Should be pretty straightforward. One you get back to (1,1) you're done.
*November 4, 2014*

**math**

If there are v,w,x,y bike, trikes, tandems and unicycles, respectively, then we know v = 32 x=y Assuming all riders wear helmets, v+w+2x+y = 57 2v+3w+2x+y = 115 32 bikes 13 trikes 4 tandems 4 unicycles
*November 4, 2014*

**Math**

(x-2)^2 can never be negative. It is its minimum value of 0 when x=2. So, the vertex is at x=2. y(2) = -3, so the vertex is at (2,-3)
*November 4, 2014*

**algebra**

the slope must be 3, so now you have a point and a slope: y-2 = 3(x-0) y = 3x+2
*November 4, 2014*

**Math Gr 12**

OK. Now what? Hint: sin x = 1/1.25 = 0.8
*November 4, 2014*

**math**

the numbers are x,x+2,x+4 x + x+2 = (x+4)^2 - 201 Now just expand, collect terms, and solve the quadratic.
*November 4, 2014*

**calculus - unclear**

Seems like we need to know something about the production of bandages. Is it continuous? Instant batches of some fixed number? Production over a period of days? Is the consumption to be considered a continuous function? I see no way to solve this with the information given.
*November 4, 2014*

**Calculus please help me**

recall your second derivative concave up if f" > 0 inflection when f" = 0 concave down if f" < 0 So, you have f"(x) = 50x(x^2+75)/(x^2-25)^3 f" < 0 on (-∞,-5) f" > 0 on (-5,0) f"(0) = 0 f" < 0 on (0,5) f" > 0...
*November 4, 2014*

**Algebr**

just the way you would evaluate any complicated expression. Start deep and work outward: f^-1(5) = 13 f^-1(13) = 2 f^-1(1) = 5 So, you have f^-1((13+2)/5) =f^-1(3) = 1
*November 4, 2014*

**Math**

f decreasing means f' < 0 f' = 18x^2 - 126x - 144 = 18(x^2-7x-8) = 18(x+1)(x-8) Since that is a parabola which open upward, f' is negative between the roots. f(x) is decreasing on the interval (-1,8) This can be verified by looking at the graph: http://www....
*November 4, 2014*

**Algebra**

f(x) = (x+5)/3 f^-1(x) = 3x-5 g(x) = 1/(f^-1(x)+1) = 1/(3x-4) g(3) = 1/5 Of course, you might also have meant just what you typed, in which case g(x) = 1/f^-1(x) + 1 = 1/(3x-5) + 1 = (3x-4)/(3x-5) and so g(3) would be 5/4
*November 4, 2014*

**maths**

I'd say it depends on what is in the bag.
*November 4, 2014*

**Algebra 1 please help answer**

you have two conversion factors: $3 = 2 lb 1 apl = 5 oz So, to convert $ to lb, do $9 * 2lb/$3 = 18/3 = 6 lb 6lb * 16oz/lb * 1apl/5oz = 96/5 = 19.2 apples
*November 4, 2014*

**Algebra 1 please help**

7 gal * 25mi/gal = 175 mi
*November 4, 2014*

**algebra**

If A has a girls and B has b girls, then we are told: a-7 = b a+4 = 2b So, a=18 b=11 That means that A had 17 boys and B had 24 boys
*November 4, 2014*

**Algebra HELP!**

x in * 1m/39.37 in = x/39.37 m y = x/39.37
*November 4, 2014*

**Math**

#1 solve for x in x(1+.18/4)^(4*5) = 30000 #2 again, x(1+.045/2)^(2*15) = 50000 #3 100*(1/2)^(15/25)
*November 4, 2014*

**geometry**

Not sure what you mean by "rows" of wires. If you just need to find the perimeter of the rectangle, that is 2(0.7+0.5) km
*November 4, 2014*

**Calculus**

if g(x) = 1/√f(2x) dg/dx = (-1/2)f(2x)^-3/2 * f'(2x) * 2 so, g'(1) = (-1/2)f(2)^-3/2 * f'(2) * 2 = (-1/2)(5^-3/2)(-1)(2) = 1 / 5√5
*November 4, 2014*

**Calculus**

#1 f' = 3x^2-8x+5 f" = 6x-8 f is concave up when f" > 0 #2 f' = 6x^2-6x-6 maybe it cannot be factored, but since the discriminant is positive, it has real solutions. Use the quadratic formula to find them. #3 you want the slope to be 3. y' = 2e^x - 3 ...
*November 4, 2014*

**mathematics**

(y,z) = (5/2, -13/4)
*November 4, 2014*

**Calculus**

f' = 6x^2+9 clearly, f' is always positive, so there are no extrema, and no intervals where f is decreasing. Just think of what you know of the curve y=x^3
*November 4, 2014*

**Calculus**

the distance z is found using z^2 = u^2 + v^2 - 2uv cos 2pi/3 what are u and v? The girl's and boy's distances, where u = -6t v = 10t z^2 = 136t^2 - 60t^2 z^2 = 76t^2 so, now you know you have to find z(1/2), and then use z dz/dt = 152 t
*November 3, 2014*

**Math**

6*36 + 4*15 = ?
*November 3, 2014*

**Math**

48+64 + 2(48+64) = 336
*November 3, 2014*

**Algebra**

just evaluate as you would anyu other expression. work your way out from the inside: f^-1(3) = 4 (because they told you that f(4) = 3) So, now you want f^-1(4) That is 7, because f(7) = 4 The final answer is 7.
*November 3, 2014*

**math**

you want to spend less than $15 to buy three books. On average, the books must cost less than how much, each?
*November 3, 2014*

**Algebra**

f^-1(x) = (x-5)/4 So, f^-1(9) = 1 f^-1(1) = -1 So, no, the answer would be -1.
*November 3, 2014*

**Algebra**

No, you can't have h^-1 with both x and y in it. In fact, there are no x's here at all. Just interchange h and y and solve for the new h: y = (1+h)/(2-h) y(2-h) = (1+h) 2y - yh = 1+h h(1+y) = 2y-1 h = (2y-1)/(y+1) So, h^-1(y) = (2y-1)/(y+1) h^-1(5) = 9/6 = 3/2 check: h...
*November 3, 2014*

**Math**

rewrite as 3/9, 4/9, 5/9, ... 1/10, 4/10, ... 3/7, 4/7, 5/7 ... the 1st and 3rd are easy, but I'd have to pick 1/5 for (b) just because it's the only one with a 5 in the denominator. No idea on the pattern.
*November 3, 2014*

**Algebra**

Lots of problems posted, with no sign of effort on your part. No ideas at all?
*November 3, 2014*

**Algebra**

x = (3y-7)/(y+1) x(y+1) = 3y-7 xy + x = 3y - 7 y(x-3) = -(x+7) y = (7+x)/(3-x)
*November 3, 2014*

**Algebra**

E(t) is just a parabola. I'm sure you know how to find the vertex, where E is a maximum.
*November 3, 2014*

**Math**

4/9 * 36 = (4*4*9)/9 = 4*4 = 16
*November 3, 2014*

**Math**

If exactly 20, then it would be 8:12 So, since we have to add 5 marbles at a time (2+3=5), the next possibility is 10:15 makes 25 marbles
*November 3, 2014*

**math**

That depends - do the minutes roll over, or not? If not, then she had to buy 400 the 1st month 400 the 2nd month 600 the 3rd month That's $50+$50+$75 = $175 If they roll over at the end of the month, then she'd have to buy less in some cases.
*November 3, 2014*

**Algebra**

the max height is achieved at the vertex of the parabola, when t = 1 for (c), just solve 16t^2 - 32t - 240 = 0 16(t+3)(t-5) = 0 ...
*November 3, 2014*

**Pre-Calc**

90 days is 90/8.1 = 11.111 half-lives, so there would be 25*(1/2)^11.111 left
*November 3, 2014*

**Math**

well, -8 < -15/2 -3 < -3/2
*November 3, 2014*

**math**

2(x+y) = 25 xy = 32 x(25-2x)/2 = 32 25x-2x^2 = 64 2x^2-25x+64 = 0 x = 3.59 y=8.91
*November 3, 2014*

**Math**

m is undefined
*November 3, 2014*

**Math**

There are several ways to write the equation, depending on the information given: slope-intercept point-slope two-point x- and y-intercepts standard form general form So, read up on these topics, and you will learn several answers to your question
*November 3, 2014*

**Maths**

since 27 = 3*9, 3a-27 = 3a-3*9 = 3(a-9)
*November 3, 2014*

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