Thursday
June 30, 2016

Posts by Steve

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

math123
42
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

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