Wednesday

June 29, 2016
Total # Posts: 41,518

**Logs**

since logs are only defined on positive numbers, we need x^2+14x > 0 x(x+14) > 0 You know that this parabola crosses the x-axis at -14 and 0, and since it opens up, it is positive everywhere except between the roots. So, the domain is (-∞,-14)U(0,∞)
*April 26, 2016*

**scte**

you forgot the frequency. anyway, once you have that, just plug in v = L di/dt and crank it out.
*April 26, 2016*

**Algebra**

2*6 = 12 (total length of pythons) 21-12 = 9 (amount left for the corn snakes) 9/3 = 3 feet per corn snake c = (21-2*6)/3
*April 26, 2016*

**Math/Precal**

(9^2x)/(27^x-2)=81^3x-4 since 9 = 3^2 and 27 = 3^3, this is 3^(4x) / 3^(3x-6) = 3^(12x-16) 4x-(3x-6) = 12x-16 x+6 = 12x-16 11x = 22 x = 2 check: 9^4/27^0 = 81^2 yep
*April 26, 2016*

**algebra**

if the steamboat's speed is s, then since time=distance/speed, 147/s = 120/(s-9)
*April 26, 2016*

**math**

I have no idea how many times she rolled the die to get the 12 twos, but since 2 only comes up on average 1/6 of the time, she can expect about 16 twos in 100 rolls.
*April 26, 2016*

**Math-check my answers!!!**

you can easily check your work by typing in your expressions at wolframalpha.com It will show how they can be simplified, and much other information as well.
*April 26, 2016*

**math**

0.10 (1+r)^(2016-1948) = 85 (1+r)^68 = 850 1+r = 1.104 r = .104 or 10.4%
*April 26, 2016*

**Math**

B = F+6 (B-22)+(F-22) = (B+F)/2 Try that. Your solution indicates that when they last met, they were 6 and 14. But 6+14 is not half the sum of their ages today.
*April 26, 2016*

**Math**

Two old friends meet. They hadn't seen each other in 22 years. Betty is 6 years older than France's, but neither is older than 50. The sum of their ages when they met is exactly half of their ages today. How old is Betty? B= F+6 B=50-22 =28 F =50 -22=28 B=28+6=34 Betty...
*April 26, 2016*

**Math**

stop guessing, and try the various functions! Just plug in a value for x and see whether the y also matches. -8*2 - 5 = -21 -8*5 - 5 = -45
*April 26, 2016*

**Math**

A? c? d? help meh
*April 26, 2016*

**Math**

nope. check again.
*April 26, 2016*

**Math**

The ordered pairs (2,-21) and (5,-45) are solutions to which of the following equations? y = -8x - 5 y = -8x + 5 <---- my answer y= 8x - 5 y= 8x + 5
*April 26, 2016*

**maths**

(2x+y+7) - (x-y) = (x-y)-2 (x-3y)-(2x+y+7) = (x-y)-2 x=2, y=-3 ...
*April 26, 2016*

**maths**

n/2 (2*2 + (n-1)(5/4)) = 204 n = 17
*April 26, 2016*

**maths**

Figure how many terms there are (n) Sn = n/2 (39+380)
*April 26, 2016*

**maths**

clearly the limit is -0.3
*April 26, 2016*

**maths**

Tn = 5 + 7(n-1) = 7n-2 S38 = 38/2 (2*5 + 37*7)
*April 26, 2016*

**maths**

do you recognize powers of 3?
*April 26, 2016*

**physics**

Let the speed of sound be s. Then the time taken for the splash to be heard is 45/s seconds. That means that the stone fell for 3.12 - 45/s seconds. You know that stone fell 45m, so 5(3.12-45/s)^2 = 45 s = 375 m/s not too close to the expected value of 343 m/s...
*April 26, 2016*

**Calc 2**

an+1/an = e^-3 (1 + 2/n + 1/n^2) that ratio is less than 1, so the series converges. see http://www.wolframalpha.com/input/?i=sum+n^2%2Fe^%283n%29
*April 26, 2016*

**Math**

44 - 0.95 * (54-34) = 25
*April 26, 2016*

**Math**

7+9=16 80/16 = 5 7:9 times 5 is 35:45
*April 26, 2016*

**math**

well, 3000 ml is 3 liters.
*April 26, 2016*

**College Algebra**

just find t where 15 e^(-0.051t) = 1
*April 25, 2016*

**algrea brs so hard**

your parentheses do not balance. is m7 m*7 or m^7 ? if all you want is to expand it, use the distributive property.
*April 25, 2016*

**math**

1/3 for each son. if each ate 1/2 of his share, then 1/2 of the pie was eaten, leaving 1/2 uneaten. You can see that the number of slices does not matter here.
*April 25, 2016*

**Maths Urgent please**

well, assuming you meant g(x) = (1/16 + x)^(-5/4) g'(x) = (-5/4)(1/16 + x)^(-9/4) using the chain rule for g(x) = u^n and u = (1/16 + x) do that again for g", and evaluate the fractions.
*April 25, 2016*

**Maths Urgent please**

so, what do you get for g'(x)?
*April 25, 2016*

**Calculus II**

Looks good to me.
*April 25, 2016*

**Calculus**

since the radius is 3/4 the height, The volume of the pile is thus v = π/3 r^2 h = π/3 (3h/4)^2 h = 3π/16 h^3 dv/dt = 9π/16 h^2 dh/dt now, plugging in your numbers, at t=3, v = 3/2, so 3π/16 h^3 = 3/2 h = 2/∛π so, 9π/16 4/∛π^...
*April 25, 2016*

**math**

huh? How much do you make on regular days? It will be 1.5 times that much.
*April 25, 2016*

**Math**

the given line has slope 1/3 so, perpendicular lines will have slope -3 The line you want is thus (using the point-slope form): y+2 = -3(x-6) or, if you prefer, y = -3x + 16
*April 25, 2016*

**Calculus II**

no, but x^(4n+2) will work. duh.
*April 25, 2016*

**Calculus II**

squaring the entire series would be (sin x)^2, not sin(x^2) Just replace all the x's with x^2. ∑(-1)^n[(x^2)^(2n+1)]/(2n+1)!
*April 25, 2016*

**Length of similar shapes**

25/10 = 5/2 all of the other dimensions are multiplied by that same ratio.
*April 25, 2016*

**Calculus**

the separation distance z after t hours is found using z^2 = (200t)^2 + (150t)^2 so, find dz/dt when t=2
*April 25, 2016*

**Math**

The medians of the triangle all pass through the center of the circle. The medians intersect 2/3 of the way to the opposite side. The altitude of the triangle is also one of the medians, and it has length 10√3. So, r = (2/3)10√3 = 20/√3 For an equilateral ...
*April 25, 2016*

**Roots, complex numbers**

huh? negatives are just numbers, like positives. z^5 = -1 = 1 cisπ z = 1^(1/5) cis(π/5) but since cisπ = cis3π = cis5π, etc., to get all the values from 0 to 2π, z = 1 cis(π/5 k) where k = 1,3,5,7,9 Reiny went over this with you. There are 5 ...
*April 25, 2016*

**Math/Precal**

sorry. I meant logy(8y-7)
*April 25, 2016*

**Math/Precal**

depends on what you mean by "solve" It is log7(8y-7)
*April 25, 2016*

**math**

depends on the table.
*April 25, 2016*

**Math**

Does 34 mean 3/4? How can Ava give 920 cranes, when she only made 100? anyway, start writing down the amounts, adding and subtracting as required. At the end, subtract Ava's from Brittany's.
*April 25, 2016*

**Math**

yep
*April 25, 2016*

**Calculus**

v = 4π/3 r^3 dv/dt = 4πr^2 dr/dt Now just plug in your numbers.
*April 25, 2016*

**Calculus**

plug and chug x^2+y^2 = 25 2x dx/dt + 2y dy/dt = 0 Now you have x, y, dx/dt, so find dy/dt
*April 25, 2016*

**Calculus**

If his distance from the pole is x and the length of the shadow is s, then s/2 = (s+x)/10 1/2 ds/dt = 1/10 (ds/dt + dx/dt) 4 ds/dt = dx/dt So, the length of the shadow is growing 1/4 as fast as the man's speed. But that's not how fast the tip of the shadow is moving. ...
*April 25, 2016*

**PHYSICS! HELIUM BALLON**

the balloon weighs 277*9.8 = 2714.6 N add to that the weight of the helium enclosed. (volume * density * 9.8) so, the volume of air displaced must weigh the same amount. Now just plug in the numbers and crank it out.
*April 25, 2016*

**Calculus**

see the other problams - they are all the same thing.
*April 25, 2016*

**Calculus**

No, they said that the radius is increasing at a constant rate of 2 cm per minute That means dr/dt = 2. dv/dt = 4πr^2 dr/dt da/dt = 8πr dr/dt You have r and dr/dt, so crank it out.
*April 25, 2016*

**Calculus**

the separation distance z after t hours is found using z^2 = (200t)^2 + (150t)^2 so, find dz/dt when t=2
*April 25, 2016*

**Trig**

for Lions, assuming that all points lie on the curve, k + Asin(0+C) = 1272 k + Asin(2B+C) = 1523 k + Asin(4B+C) = 1152 k + Asin(6B+C) = 891 I'd start by noting that sin(C) = (1272-k)/A Now you can find cos(C) and then use the sum formulas to expand the other sines.
*April 25, 2016*

**O.D.E**

If someone can help me with this ODE I would greatly appreciate it. Thank you in advance! ------ Consider the differential equation dx/dt = 1/2x This is a separable O.D.E., so we know how to find all of its solutions: they are of the form x(t) = sqrt(t+c) where C is a constant...
*April 25, 2016*

**CALCULUS**

the small tank has a volume of 96π ft^3 its depth decreases at a rate of (1/2)/(16π) = 1/(32π) ft/s So, A: v(t) = 96π - 1/2 t B: duh C: the large tank's area is 4 times as big, so its depth increases 1/4 as fast, or 1/8 ft/s. D: 6/(192π)
*April 25, 2016*

**Brokport**

If the amounts invested are x,y,z then they have told us that x+y+z = 180000 .08x + .06y + .09z = 8520 .08x = 6 * .06y I suspect a typo, since even if the whole amount were invested at 6%, the interest would be 10,800. In other words, there's no way to solve these ...
*April 25, 2016*

**Algebra SOLVING LINEAR EQUATIONS AND INEQUALITIES**

#1 you can solve for 1/x and 1/y in the usual ways: elimination: double the 1st and subtract 6/x - 4/y = 28 6/x + 3/y = 7 ------------------- 7/y = -21 1/y = -3 then, 1/x = 8/3 or, y = -1/3 and x = 3/8 using substitution, 3/x = 14+2/y 2(14+2/y) + 3/y = 7 28 + 4/y + 3/y = 7 7/y...
*April 25, 2016*

**Math**

(2)(33)(19)[2(33)(19)-33-19] (2)(33)(19)[1254-33-19] (2)(33)(19)[1202] 1,507,308
*April 25, 2016*

**geometry**

Find the volume in terms of pi of a sphere with a surface area of 9 pi sq ft
*April 24, 2016*

**Math2**

f(x) = 3x^2 - 12x + 2 the y-intercept is clearly at 2. x-intercepts? where y=0. Use the quadratic formula to get x = 2±√(10/3)
*April 24, 2016*

**Math**

3 : 2 = 1 : 2/3 = 5 : 10/3
*April 24, 2016*

**Algebra**

slope = 15/9 = 5/3 y-4 = 5/3 (x-6) y = 5/3 x - 6 The lines are not perpendicular, because the slopes are not negative reciprocals. The line through the points is perpendicular to y = -3/5 x - 6 However, they do both have a y-intercept of -6.
*April 24, 2016*

**Math**

using the vertex form, y = a(x-3)^2 - 6 using the point given, 10 = a(-1-3)^2 - 6 10 = 16a-6 a = 1 y = (x-3)^2 - 6 = x^2-6x+3
*April 24, 2016*

**math**

clearly getting a 44 (lower than any of her scores so far) will not raise her grade!! Add up the total points she has so far. A "B" average for 7 tests needs at least 80*7 = 560 points. So, how many does she need to get there?
*April 24, 2016*

**Math**

The sequence is not geometric! 17111/19 = 900.5789 1539121/17111 = 89.9492 the ratio is not constant. Fix it, find the common ratio r, and then a6 = 19*r^5
*April 24, 2016*

**Calculus quick question pls**

huh? huh? How can you say that? x^2 is always positive, right? At least it is never negative. So, x^2+1 is always positive, and always at least 1. So, dividing by x^2+1 will never yield a vertical asymptote.
*April 24, 2016*

**Calculus quick question pls**

vertical asymptotes occur when you try to divide by zero. x^2+1 is never zero. You solved for x^2-1 = 0
*April 24, 2016*

**Math**

surely you can do the math. ∫[2,3] (3x^2)-(x^4-10x^2+36) dx = ∫[2,3] -x^4 + 13x^2 - 36 dx = -x^5/5 + 13/3 x^3 - 36x [2,3] = (-243/5 + 13*27/3 - 36*3)-(-32/5 + 13/3 * 8 - 36*2) = 62/15 double that for 124/15 Now you need to ask your teacher how 1436/15 can be right...
*April 24, 2016*

**Math**

what's the trouble? You are adding up a bunch of thin rectangles, with width dx and height the distance between the curves. The curves intersect at (±2,12) and (±3,27). Since both functions are even, we can use symmetry and use a = 2∫[2,3] (3x^2)-(x^4-...
*April 24, 2016*

**Absolute and relative change**

Nope. 1.07x = 16.05 the 16.05 includes the tax, right?
*April 24, 2016*

**math**

30P4 = 30*29*28*27
*April 24, 2016*

**math**

4! = 24
*April 24, 2016*

**Maths**

words, words, words. This is math, so use math 4x^2-5x+7 terms are separated by + and - signs, so there are three terms
*April 24, 2016*

**math(counting)**

if all you want is permutations of the letters, MAIRE: 5! = 120 OISEAU: 6! = 720 If you want your anagrams to be actual words, then of course there will be a lot fewer. Better get a good French dictionary.
*April 24, 2016*

**math(counting)**

what does "near" mean? There are only 5 kids, after all.
*April 24, 2016*

**Math**

If she started out with x, and was left with 15 more than half of what she started with, then x - x/8 - x/5 - x/10 = x/2 + 15 x = 200
*April 24, 2016*

**Ic**

I assume you can handle the java syntax, but the flow of logic is integer a,b,c,option,err print "Enter two integers: " read a,b print "Enter option: 1: add 2: subtract 3: multiply 4: divide " read option err=0 case option { 1: c=a+b 2: c=a-b 3: c=a*b 4: if...
*April 24, 2016*

**math**

233489
*April 24, 2016*

**precalc**

oops. tanϕ = -1/√15 tan(θ+ϕ) = (√8 - 1/√15)/(1-(√8)(-1/√15)) = (32√2 - 9√15)/7 = 1.48
*April 24, 2016*

**precalc**

cos(θ) = −1/3 QIII, so tanθ = √8 sin(ϕ) = 1/4 in QII, so tanϕ = -√15/4 tan(θ+ϕ) = (tanθ + tanϕ)/(1-tanθ tanϕ) = (√8 - √15/4)/(1-(√8)(-√15/4)) = (18√15 - 31√2)/52
*April 24, 2016*

**Absolute and relative change**

6%
*April 23, 2016*

**Precal/Math**

log(3-2x)-log(x+24)=0 log (3-2x)/(x+24) = 0 (3-2x)/(x+24) = 1 3-2x = x+24 x = -7
*April 23, 2016*

**geometry**

Thye area of a regular hexagon is 38 cm^2. What is the area of a regular hexagon with sides 4 times as long?
*April 23, 2016*

**Calculus!!**

dy/dx = xy/2 dy/y = x/2 dx ln y = 1/4 x^2 + c y = c e^(x^2/4)
*April 23, 2016*

**AP Calculus**

A yes, if f"=0 and f'≠0 B find g'(0) Then the tangent line is y-5 = g'(0) (x-0)
*April 23, 2016*

**Calculus**

The large cylinder has a cross-section 4 times that of the smaller one, so its water level rises 1/4 as fast as it falls in the smaller one.
*April 23, 2016*

**Calculus**

A a = ∫[0,5] 3/e^x dx = 3 - 3/e^5 B now you want c such that ∫[0,c] 3/e^x dx = ∫[c,5] 3/e^x dx 3 - 3/e^c = 3/e^c - 3/e^5 6/e^c = 3 + 3/e^5 e^c = 2/(1+e^-5) c = ln 2/(1+e^-5) C each semicircle has diameter equal to y. Adding up all those thin slices of ...
*April 23, 2016*

**math**

not sure what H= 10 inches from measuring the perimeter of the base is 2 inches means
*April 23, 2016*

**AP Calculus**

A (1+x)y^3 + (x^4)y - 85 = 0 y^3 + 3(1+x)y^2y' + 4x^3y + x^4y' = 0 y' = -(y^3+4x^3y)/(3(1+x)+x^4) = -(y^3+4x^3y)/(x^4+3x+3) B y'(3) = -109/93 So, the tangent line is y-1 = -109/93 (x-3) C y(3) = 1, so g(1) = 3 g'(1) = 1/y'(3) = -93/109
*April 23, 2016*

**GEOMETRY HELP PLEASE**

well, maybe not. It just might mean that AB is shorter than CD. In that case, h = 3√5 and x = -2, so CD=8 and AB=4, making the area (8+4)/2 (3√5) = 18√5
*April 23, 2016*

**GEOMETRY HELP PLEASE**

Drop altitudes CE and DF The trapezoid now can be seen to be rectangle CDEF and two right triangles of height h and base x. h^2+x^2 = 7^2 h^2 + (8+x)^2 = 9^2 Hmmm. I get x = -2 I guess I have drawn the figure incorrectly. Maybe you can use my ideas in your own drawing.
*April 23, 2016*

**math**

L = K∛M 15 = K∛125 15 = K*5 3 = K
*April 23, 2016*

**converting parabolic equations**

x = 8(y-1)^2-15 x = 8(y^2-2y+1)-15 x = 8y^2-16y-7
*April 23, 2016*

**physics**

So, if their ratio is 1.1, you have determined that Ve/Vb = 1.1 since distance = speed * time 3*10^-9 Ve = 1.1*3*10^-9 Vb = 3.3*10^9 Vb So, De-Db = 0.3*10^-9 Vb
*April 23, 2016*

**Calculus**

c'mon, you can do this. dm/dt = -0.22m dm/m = -0.22 dt ln(m) = -0.22t + c m = c e^(-0.22t) c is the initial amount, so m(t) = 20 e^(-0.22t) I'm sure you can find the half-life now, ok?
*April 23, 2016*

**Calculus**

we know the slope is dy/dx, so at (1,2), the slope is -3. The tangent line is thus y-2 = -3(x-1) y dy = -6x^2 dx 1/2 y^2 = -2x^3 + c y = √2 √(c-2x^3) you know that the domain of √ is non-negative numbers, so c-2x^3 >= 0 2x^3 <= c x <= ∛(c/2)
*April 23, 2016*

**Calculus**

recall that for parametric curves, the curvature is x'y" - x"y' ----------------- (x'^2 + y'^2)^(3/2) so, for your function, that is x' = 2t x" = 2 y' = 2t^2 y" = 4t (2t)(4t)-(2)(2t^2) ----------------------- = 4t^2/(8t^3(1+t^2)) = 1...
*April 23, 2016*

**Pre-Calc**

the domain of log(u) is u>0, regardless of the base of the logs. So, you need 3x-8 >0 x > 8/3 or, (8/3,∞)
*April 23, 2016*

**maths**

also, we have (x+y)(x-y) = 12 The pairs of factors of 12 are 1,12 2,6 3,4 x+y=6 x-y=2 x=4,y=2
*April 23, 2016*