Monday
December 5, 2016

Posts by Steve

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

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