Monday

December 5, 2016
Total # Posts: 46,840

**math**

f = e^(x^2-2x) f' = (2x-2) e^(x^2-2x) since e^(x^2-2x) is always positive, f'=0 at x=1 f" = (4x^2-8x+6)e^(x^2-2x) f"(1) > 0 so f(1)=1/e is a local minimum. Now just check f(0) and f(2) to find the absolute extrema for the interval.

*November 3, 2016*

**maths**

(a) Find the points which divide the line joining A(1,3) and B(-4,-1) internally in the ratios: (ii) 1:1 (iii) 3:1 (b) On the same x-y axes plot the point A(1,3) and B(-4,-1) and draw the line joining them. Add the three points which you calculated in part (a).

*November 3, 2016*

**math**

sinA = 1/2 cosA = ?3/2 tanA = 1/?3 plug those in and see where it takes you

*November 3, 2016*

**Math**

1/2 in:4 ft = 5/2 in:20 ft

*November 3, 2016*

**calculus**

v^2 = rg tan(?) 2v dv/dt = rg sec^2(?) d?/dt

*November 3, 2016*

**calculus**

If x is the distance from the closest point on the wall, x/50 = tan? 1/50 dx/dt = sec^2(?) d?/dt

*November 3, 2016*

**calc**

If the light is at height h, we know that 6/12 = h/18 h = 9 So, if the shadow has length s when the man is x feet from the pole, then we have s/6 = (x+s)/9 s = 2x so, ds/dt = 2 dx/dt Now just plug in your numbers.

*November 3, 2016*

**calclus**

draw a diagram. If x feet of line are out, 15/x = sin? -15/x^2 dx/dt = cos? d?/dt Now just plug in your numbers.

*November 2, 2016*

**Calculus**

By inspection, f(10)=40, so f^-1(40) = 10 finding f^-1(x) is quite hard, since you have to solve a cubic. http://www.wolframalpha.com/input/?i=inverse+2x%E2%88%9A(x-6)

*November 2, 2016*

**Calclus**

well, dy/dt = -2x/(1+x^2)^2 dx/dt so plug in x = -2

*November 2, 2016*

**Algebra**

there are many: (1,4) (10,0) (-5,22) and lots lots more

*November 2, 2016*

**time speed and distance**

Break the total time into three periods: x: when a&b are on the bike y: when a rides back for c z: when a&c are on the bike since distance = time*speed, write the net distances traveled by each person: a: 50x-50y+50z = 40 b: 50x+10y+10z = 40 c: 10x+10y+50z = 40 Now solve for x...

*November 2, 2016*

**math**

v = 3495 - (3495/5)t

*November 2, 2016*

**Calculus**

v = 4/3 pi r^3 dv/dt = 4 pi r^2 dr/dt Now just plug in your numbers.

*November 2, 2016*

**Math**

break them into x- and y-components, then add. Then convert back to polar form. F1+F2 = <5/2,5?3/2>+<0,8> = ?

*November 2, 2016*

**Math**

1/7 * 9/8 = 9/56

*November 2, 2016*

**Math**

huh. I saw the ? and thought of vector differentiation. But the set of elements and the v5 throw me. Care to explain what this is all about?

*November 2, 2016*

**Adv function**

divide top and bottom by cos^2 (multiply by sec^2) and you have sec^2(x)/(1-tan^2(x))

*November 2, 2016*

**Math**

((?2 x) + k)^2 = 2x^2 + 2?2 kx + k^2 So, we need k=±5 That means a = ±10?2

*November 2, 2016*

**Math**

what is 8^2 + 2^2 ?

*November 2, 2016*

**Maths**

I will assume that you plugged in 5 for x to justify your answer.

*November 2, 2016*

**math**

If it takes x quarts to paint the inside, then you have x + x+19 = 107 Now adjust that so it answers the question.

*November 2, 2016*

**Plane Trigonometry**

Draw your triangles. You will then see that sinA = -4/5 cosA = 3/5 sinB = -3/7 cosB = -?40/7 Now just plug those into the formula for cos(A-B)

*November 2, 2016*

**Math**

If they lost x games, then x + x+17 + 3 = 52

*November 2, 2016*

**Math, Precalc**

It's annoying how you don't want to show your work. Just let us take care of it all. Just for readability, try letting u = 1/x. Then you have 6*(9^u)-13*(6^u)+6*(4^u))=0 6*3^(2u) - 13*3^u*2^u + 6*2^(2u) Now if you let v=3^u and z=2^u you have 6v^2 - 13vz + 6z^2 = 0 (3v...

*November 2, 2016*

**Math, Precalc**

You have powers of 2 and 3. Expand all the groups, collect the powers, and solve for x. If you get stuck, show what you got done.

*November 2, 2016*

**Plane Trigonometry**

draw your triangles in standard position. It will be clear that sinA = 4/?41 cosA = -5/?41 sinB = -12/13 cosB = -5/13 Now just plug that into the formula for cos(A+B) Although I suspect a typo...

*November 2, 2016*

**geography**

if you google those choices including the word "Iran", it should be clear.

*November 2, 2016*

**geometry**

geez. Just look at the diagram. It should be clear what part of the triangle is used. No idea at all? And sorry, can't do constructions here. I'm sure google can help out though.

*November 2, 2016*

**algebra 2**

and ... ? Don't make us figure out the question, as well as the answer!

*November 2, 2016*

**PLZ CHECK ANSWERS**

#11. Nope. Your answer is -3 7/9 + 1 2/9 #12. Nope. 6 1/3 - 4 4/9 = 6 3/9 - 4 4/9 = 5 12/9 - 4 4/9 = ...

*November 2, 2016*

**Math**

Actually, Lebanon had the smallest population! And it is customary to write 10^6 for a power, since yours looks like just the number 106.

*November 2, 2016*

**plz plz help me belive me have tried**

I am Leo I Just changed my name to Steve because I thought I'd get in trouble

*November 2, 2016*

**plz plz help me belive me have tried**

Let A = (X+Y)/2 and B = (X-Y)/2. a = sin X + sin Y = sin(A+B) + sin(A-B) = 2 sin A cos B b = cos X + cos Y = cos(A+B) + cos(A-B) = 2 cos A cos B a/b = (2 sin A cos B) / (2 cos A cos B) = tan A sin A = a/?(a² + b²) cos A = b/?(a² + b²) sin(X+Y) = sin 2A = 2...

*November 2, 2016*

**Oops^2**

Holy smoke! I just noticed another typo. The correct solution is: 3/(1 1/4) = 3/(5/4) = 3 * 4/5 = 12/5 = 2 2/5 But I'm sure you already figured it out ...

*November 2, 2016*

**Oops**

I see that my answer is not one of the choices. Can you see my typo? 16/5 = 3 1/5, not 5 1/3 Never think you're done just because you arrived at answer. Always check it!

*November 2, 2016*

**MATH STEVE**

suppose I asked you how many pieces of 3 ft each you could cut from a 15-foot string. How would you do it? Divide the total length by the length of each piece, right? Same here. Don't be flummoxed by the fractions -- they're just numbers like any others. 3/(1 1/4) = 3...

*November 2, 2016*

**maths**

The net for a unit cube has a perimeter of 14. So, yours has a perimeter of 70

*November 2, 2016*

**Math (Help!)**

I don't know what to do either, since all you dis was post an expression with no question. If you want to see what it simplifies to, do multiplication first, then addition: 5x2+6-5 = 10+6-5 = 16-5 = 11 If you really have no clue, you seriously need to review the material ...

*November 2, 2016*

**Math**

0 < 1/9 < 1/4, so it rounds to 0 1/2 < 14/27 < 3/4, so it rounds to 1/2

*November 2, 2016*

**Calculus**

f' = 4x^2 f = 4/3 x^3 + C Since f(-1)=3, (4/3)(-1)+C = 3 C = 13/3 So, f(x) = 4/3 x^3 + 13/3 do the other one in like wise.

*November 2, 2016*

**Math**

is there a question in there somewhere?

*November 2, 2016*

**maths steve reiny**

?x^?x = 2 Let u = ?x. Then u^u = 2 Solving that does not yield to algebra. Better try a graphical method. You will get x ? 2.43238

*November 2, 2016*

**Math, Precalc**

just start by combining like powers: (3^x)+(5^{x+3})=(3^{x+4})-(1/3)*( 5^{x+2}) 3^x + 125*5^x = 81*3^x - 3^-1 * 25*5^x 3*3^x + 375*5^x = 243*3^x - 25*5^x (375+25)*5^x = (243-3)*3^x 400*5^x = 240*3^x 5*5^x = 3*3^x 5^(x+1) = 3^(x+1) (x+1)log5 = (x+1)log3 (x+1)(log5-log3) = 0 x = -1

*November 2, 2016*

**Algebraic linear equations**

Since the total distance is y, if she walks a distance w, then she runs the rest of the way (y-w). since time = distance/speed, and her total time is 2/5 hours, w/4 + (y-w)/8 = 2/5 2w + y-w = 16/5 w+y = 16/5 w = 16/5 - y w = (16-5y)/5

*November 2, 2016*

**math**

what is a one-sided tunnel? how do vertical walls have a diameter? Maybe you could describe the shape of the tunnel cross-section. Heck, in doing so, you might actually see how to solve the problem...

*November 2, 2016*

**Math**

so, can you describe the associative property? What does it mean about groping numbers for addition?

*November 2, 2016*

**math**

naturally, 5 times the perimeter.

*November 2, 2016*

**Gaussian Elimination Method**

Your equations are mangled, but this web site will show the operations in detail: http://matrix.reshish.com/gauss-jordanElimination.php

*November 2, 2016*

**Physics**

uh, what is your first guess?

*November 2, 2016*

**Calc**

no sweat. Just expand the integrand and you have sec(y) tan(y) - sec^2(y) Those look familiar?

*November 2, 2016*

**Physics**

hint - it decelerates at half the rate it accelerated. Now recall your basic equation of motion: s(t) = vt + 1/2 at^2 and apply it to the three intervals.

*November 2, 2016*

**math**

recall that the circle with center at (h,k) and radius r has equation (x-h)^2 + (y-k)^2 - r^2 The radius here is the distance from the center to (4,-1). Now just plug in your numbers.

*November 2, 2016*

**Calculus**

using similar triangles, if the person is x feet away, and the shadow has length s, s/5 = (x+s)/20 4s = x+s x = 3s so, dx/dt = 3 ds/dt that means ds/dt = -8/3 ft/s So, the shadow is shrinking as the man is walking, so the tip is moving at the rate of -(8 + 8/3) = -32/3 ft/s ...

*November 2, 2016*

**Pre-algebra**

you cannot. Only by dividing by some multiple of pi (or subtracting pi) can you get a rational result. pi - pi = 0 -- rational pi/2pi = 1/2 -- rational

*November 2, 2016*

**Math**

generally, yes. However, if it registers temperatures below 0, then negative numbers will have to be included, meaning integers, not just whole numbers.

*November 2, 2016*

**maths**

If the side of the field has length x, then 4x = 2000/40 = 50 x = 25/2 80 * (25/2)^2 / 100 = 125

*November 2, 2016*

**Math**

since time = distance/speed, 350/x = (470-350)/(x-15)

*November 2, 2016*

**Math**

Just plug and chug ?Cz dx + x dy + y dz = ?[0,1] (t^4)(4t^3) + (t^4)(5t^4) + (t^5)(4t^3) dt = ?[0,1] 4t^7 + 9t^8 dt = 1/2 t^8 + t^9 [0,1] = 1/2 + 1 = 3/2

*November 2, 2016*

**Math**

F·dr = sinx dx + cosy dy + xz dz Now just crank it out, using the definitions of x,y,z: ?4t^3 sin(t^4) - 3t^2 cos(t^3) + (t^4)(t) dt = -cos(t^4) - sin(t^3) + 1/6 t^6 [0,1] = -1 + 1/6 = -5/6

*November 2, 2016*

**Math**

this is just like the others. W = ?F•dr see the other posts.

*November 2, 2016*

**Geometry (Please check my work)**

Nope. Reflecting across the line y = -5 means that the image is as far below the line as (-2,-1) is above it: 4 units. So, (-2,-1) -> (-2,-9) Same with the line x=1. 3 to the left, so 3 to the right. (-2,-9) -> (4,-9) Reflecting across the line y=k: (x,y) -> (x,k-(y-k...

*November 2, 2016*

**math**

a number divided by 3

*November 2, 2016*

**Algebra 2**

none

*November 2, 2016*

**Math**

500,000 * 1.04^3

*November 2, 2016*

**Maths**

If the number of sides is n, then we have 180(n-2)/n = 10(360/n)-84 n=15 So, the sum of its interior angles is 180(15-2) = 2340°

*November 2, 2016*

**@Writeacher**

Writeacher, you're all right! =)

*November 2, 2016*

**math**

well, did you look at the formula? If a line with slope m passes through (h,k), its equation is y-k = m(x-h) So plug in your numbers.

*November 2, 2016*

**Maths**

Those numbers make no sense, either as absolute quantities or as percentages.

*November 2, 2016*

**Algebra**

The others are 180-(5x-20) = 200-5x or 180-(70-4x) = 110+4x In either case, opposite angles are equal, so if you want the actual numeric measure, just set the two expressions equal, solve for x, and the evaluate the expressions.

*November 2, 2016*

**Math**

v(t) = 6t^2 + ? a(t) = 12t + ? The ? is because you did not specify the power of t for the "45" term Anyway, fill it out and use your numbers. scrub...

*November 2, 2016*

**Math**

so, why don't you show us what you did? If you meant n/-3 + 5 >= 4 just work it as usual: subtract 5 n/-3 >= -1 Now multiply by -3 and change direction n <= 3 The reason you change direction is just a shortcut for moving things around by addition and subtraction: ...

*November 2, 2016*

**Mathematics**

the slope is -2, so y-5 = -2(x-1) y = -2x+7 2x+y = 7 2x+y-7 = 0 x/(7/2) + y/7 = 1 take your pick

*November 2, 2016*

**piedad elementary school**

try dividing out the common factor: 100/300 = 1*100/3*100 = 1/3 * 100/100 = 1/3 and so on. You will find one of the fractions has no common factor to use.

*November 2, 2016*

**maa central**

#blue / #total = 5/10

*November 2, 2016*

**Calc III**

Using symmetry, you can just take 4 times the volume in the 1st octant: 4?[0,?/2]?[0,4cos?]?[0,?(16-r^2)] r dz dr d? = 4?[0,?/2]?[0,4cos?] r?(16-r^2) dr d? = -4/3?[0,?/2] (16-r^2)^(3/2) d? [0,4cos?] = -4/3?[0,?/2] (64sin^3?)-(64) d? = -256/3?[0,?/2] sin^3?-1 d? = 256/3 ?[0,?/2...

*November 2, 2016*

**Math**

I assume you want to simplify in some manner. 7(4log2-(log3+log5)) + 5(2log5-(3log2+log3)) + 3(4log3-(4log2+log5)) now combine like logs, and you wind up with log2 Or, you can combine the factors first: 7log16/15+5log25/24+3log81/80 log ((2^4/(3*5))^7 * (5^2/(2^3*3))^5 * (3^4...

*November 2, 2016*

**math**

recall the multipliers of Pascal's Triangle: 1 3 3 1 Now use those in the expansion.

*November 2, 2016*

**Ad.func**

Let x = the distance from the wall a = angle of elevation of the bottom of the picture b = angle subtended by the picture Then we have 1/x = tan(a) 4/x = tan(a+b) we want b = pi/6. So, (tana + tanb)/(1-tana*tanb) = 4/x Now just plug in 1/x for tan(a) and solve for x

*November 1, 2016*

**9th grade algebra (factoring with quadratic)**

#7: x^2 - 18x + 57 = 0 Looks like the quadratic formula is what you'll need: x = 9±?24 Or, you could complete the square, as was done in the following problems: x^2 - 18x + 57 = 0 x^2 - 18x + 81 = 24 (x-9)^2 = ±?24 x = 9±?24 The rest look good, except ...

*November 1, 2016*

**Trigonometry**

amplitude is (95-80)=15 center line is 80, so start with the assumption that the minimum occurs at midnight (0 hours): y = -15cos(kx)+80 The function has a period of 24 hours, so 2?/k = 24, making k=?/12 y = -15cos(?/12 x) + 80 Now we know that the max occurs at x=15, not x=12...

*November 1, 2016*

**Math**

First, be sure that f(0)=f(1). It does since f'(x) = 3x^2-4x+1 = (3x-1)(x-1) just find a value in the interval [0,1] where f'(x) = 0. Now it's just algebra. The calculus is done.

*November 1, 2016*

**Math**

It appears that g(x) is constant, so it does not matter what f is. Fix the typo. Then just substitute f(x) for x in the definition of g. (g?f)(x) = g(f(x)) That is, if g(x) = x+3, (g?f)(x) = g(f) = f+3 = 4x-5+3 = 4x-2

*November 1, 2016*

**maths**

well, there are 42 eggs in total. Now work out the rest, based on that.

*November 1, 2016*

**algebra**

the total round-trip distance is 2 * 4 2/3 = 9 1/3 so, ...

*November 1, 2016*

**Business math**

He gets 2 years of interest on the original 500, and 1 year on the extra x. So, we want 500(1 + .085/2)^(2*2) + x(1 + .085/2)^(2*1) = 1000

*November 1, 2016*

**maths**

clearly David had 75 oranges. The rest then can be easily found.

*November 1, 2016*

**Math**

If the larger radius is r, then we have ?r^2 = ?(r-3)^2 + 15? r^2 = r^2-6r+9 + 15 6r = 24 r = 4 check: 16? = ? + 15?

*November 1, 2016*

**Math**

no digit can be 10.

*November 1, 2016*

**Chem**

It's hard to understand why you ask such a general-knowledge question here, rather than just going first to google. This would be a good place to start, both for the information, and the explanations on why the above question is rather ill-formed. https://www.webelements....

*November 1, 2016*

**English**

while syntactically gerunds are equivalent to infinitives in these uses, in practice, I doubt you will find anyone using the constructions in 2 and 4. I have heard #6. I guess because the word preceding the gerund is an adjective rather than a noun. #7 and 8 are both common, ...

*November 1, 2016*

**Science**

the acceleration indicates how much the velocity changes each second. Hence, v = at (m/s) = (m/s^2)(s)

*November 1, 2016*

**Math**

26 * 5 = 130

*November 1, 2016*

**Math**

12 + 14 = 26 * 5 This method is way easier

*November 1, 2016*

**hellllllpppp**

23/63 = 36% So

*November 1, 2016*

**hellllllpppp**

Damon is an uneducated tutor

*November 1, 2016*

**hellllllpppp**

He is un educated

*November 1, 2016*

**math**

LCM(84,35,52) = 5460

*November 1, 2016*

**MATH**

14f + 6e - 51

*November 1, 2016*

**MATH**

14f - 30 - 15e

*November 1, 2016*