Friday
December 19, 2014

Posts by steve


Total # Posts: 27,623

algebra
y = ab^x a*b^2 = 3 a*b^9 = 33 a = 3/b^2, so a*b^9 = 3/b^2 * b^9 = 3b^7 = 33 b = 11^(1/7) a = 3/11^(2/7) y = 3/11^(2/7) * 11^(x/7) = 3*11^((x-2)/7) y(15) = 3*11^(13/7) = k
November 12, 2014

math olympiad
there are many such rectangles. 1 x √88 2 x √85 ... √44 x √45
November 12, 2014

intermediate algebra
the line through (2,3) and (2,0) is x = 2 That is a vertical line. So, the perpendicular line through (2,3) is y = 3
November 12, 2014

Maths
h/10 = 1.8/1.2
November 12, 2014

St Ans School
75-x = x-45 ...
November 12, 2014

Math
How about writing that as 3x - 8y - 4 = 0
November 12, 2014

Math Help
ln√x-8=5 ln√x=13 √x = e^13 x = e^26 log2x+log2(x+2)=log2(x+6) log2(x(x+2)) = log2(x+6) x(x+2) = x+6 x^2+2x = x+6 x^2+x-6 = 0 (x-2)(x+3) = 0 x = 2 or -3 But, log2(x) is not defined for x <= 0, so x=2 is the only solution check: log2(2)+log2(2+2) = log2(2+6...
November 12, 2014

Math
if course not "all reals" plug in just some value and see whether the equation balances. In particular, try x=0: log(4) =?= log(2) I don't think so. What you need to realize is that if 2^x = 2^y or log2(x) = log2(y) or 2x = 2y or 2+x = 2+y or in general, for any ...
November 12, 2014

Maths
1.3/1.8 = h/(7+1.8)
November 12, 2014

Math
you want e^.12x = 3
November 12, 2014

maths
a:b = 3:5 = 12:20 b:c = 4:7 = 20:35 a:b:c = 12:20:35
November 12, 2014

math algebra
Hard to tell, but it appears that you have (x-3)/4 - (y-2)/5 = -1/4 (4-x)/3 + (3-y)/2 = -13/20 which is the same as 5x - 4y = 2 20x + 30y = 209 20x-16y = 8 20x+30y = 209 46y = 201 so, x = 448/115 y = 201/46 Hmmm. Maybe you had x - 3/4 - y - 2/5 = -1/4 4 - x/3 + 3 - y/2 = -13/...
November 12, 2014

Pre-Calculus
recall that cos 2x = cos^2 x - sin^2 x
November 12, 2014

Pre-Calculus
7/12 = 1/3 + 1/4 now review your addition formula for tan(x+y)
November 12, 2014

Pre-Calculus
recall that cos(x-y) = cosxcosy+sinxsiny hence the name cosine -- sine of complementary angle
November 12, 2014

maths
we need (1+x)(0.9) = 1.08 x = 0.20 = 20% check: on $1.00 cost, mark up to $1.20 discount = $0.12, so the final price is $1.08, or 8% profit
November 12, 2014

Pre-Calculus
cos(cos^2+sin^2) don't forget your Algebra I now that you're taking trig!
November 12, 2014

Math
surely the explanation in your text will be more thorough than any offered here. Also, google is your friend...
November 12, 2014

Geometry
s = rθ, so θ = s/r
November 11, 2014

math
12 and 15
November 11, 2014

math
yes, you did
November 11, 2014

Calculus
just use the power rule: d/dx(x^n) = n x^(n-1) so, f'(x) = 3x^2 + 5/x^2
November 11, 2014

Geometry
No, it's November 11. I think you need to provide a little more context. p -> q where p=It's snowing today and q=It is December
November 11, 2014

math
Assuming that's $2.90 each, then 2*2.9 = 5.80 So, now, which has cost more for two packs of batteries?
November 11, 2014

calculus related rates
PV = k V dP/dt + P dV/dt = 0 dP/dt = -(P/V) dV/dt Now just plug in your numbers. By the way, this is true only if the temperature remains constant. More generally, PV = kT
November 11, 2014

calculus inverted cone
when the contents have depth y, the radius of the surface of the liquid is y/2 So, v = pi/3 r^2 y = pi/3 (y/2)^2 y = pi/12 y^3 dv/dt = pi/4 r^2 dy/dt Now just plug in your numbers.
November 11, 2014

Math
e+s = 80 e-17 = 2(2/3 s) Now just solve for e and s, and then get e-s.
November 11, 2014

Math
looks ok. But that depends on what x represents...
November 11, 2014

Math
9^2+35
November 11, 2014

Math
5 * 50/(5+8+7) = 12.5 m
November 11, 2014

College Algebra
there are lots of good graphing sites. Try here: http://www.wolframalpha.com/input/?i=plot+y%3D1%2F2x-3 The two equations describe the same line.
November 11, 2014

Advanced Algebra
3x=4(4-2x)=11 I suspect a typo
November 11, 2014

Pre-Calc/Trig
extrema where 12x^2 - 24x = 0 12x(x-2) = 0 Now apply the 2nd derivative test, and what you know about the general shape of cubics.
November 11, 2014

math
I suspect that V = XYZ So, just multiply the three values
November 11, 2014

Calculus
Go to http://www.wolframalpha.com/input/?i=8ln%28sec%28x%29%29+ and scroll down a bit.
November 11, 2014

Derivatives
Hmmm. You have y = uv, so y' = u'v+uv' = 3x^2(5x-1)^4 + x^3 * 4(5x-1)^3(5) = x^2(5x-1)^3 (3(5x-1) + 20x) = x^2(35x-3)(5x-1)^3
November 11, 2014

Geometry
if the circle has diameter d, then the square has sides equal to the diameter. area = d^2
November 11, 2014

Pre-Calc/Trig
x^5 is positive for x>0 and negative for x<0. So, the graph curves down on the left, and up on the right. All you really need to look at is the highest power of x, which dominates everything for large values of x.
November 11, 2014

math - oops
Oops. That is Nx - My I'll let you make the change and redo the arithmetic.
November 11, 2014

math
Green's Theorem says that ∮CMdx+Ndy = ∫∫RMx+Ny dx dy Nx = 8xy My = 2xy So, we end up with ∫[0,2]∫[x,2x] 10xy dy dx = ∫[0,2] 5xy^2 [x,2x] dx = ∫[0,2] 5x(4x^2-x^2) dx = ∫[0,2] 15x^3 dx = 5x^4 [0,2] = 80
November 11, 2014

algebra 2
Just as with normal fractions, you need to find a common denominator. For example, with 2/3 + 3/5, the commond denominator is (3)(5) Here, you will have a common denominator of (x+y)(x-y) So, you will wind up with (x-y)(x-y)/(x+y)(x-y) + (x+y)(x+y)/(x-y)(x+y) = [(x-y)^2 + (x+y...
November 11, 2014

math
telepathy
November 11, 2014

Algebra please help answer ASAP
(A) 5km/.5hr = 10.0 km/hr (B) 20km/.8hr = 25.0 km/hr (C) 10.0+25.0 = 35.0 km
November 11, 2014

Algebra please help answer thx
1/4 of the guitarists play jazz, so 3/4 play classical. So, 3/4 * 5/8 * 64 = 30
November 11, 2014

math
you are correct, because 6 and23 have no common factors
November 11, 2014

math
every 12 minutes both change at the same time.
November 11, 2014

Math
every 35 days the schedules coincide
November 11, 2014

Precalc/Trig
The first 4 are all ok cot is negative in QII and QIV, and you are right about π±θ. But, that θ is the reference angle, which is always in QI. θ = arccot(5), not -5.
November 11, 2014

Math
(-x+4)log11 = (3x-2)log5 -log11 x + 4log11 = 3log5 x - 2log5 -(log11+3log5)x = -(2log5 + 4log11) x = (2log5+4log11)/(log11+3log5) and, of course, you could go on and say x = log(5^2*11^4)/log(11*5^3) = log366025/log1375 or even log1375366025
November 11, 2014

Grammar
more in keeping with the original might be: The medication had a noticeable positive effect on the patient.
November 11, 2014

physics
Snell's Law says that sinθ/sin30° = 1/1.33
November 11, 2014

math
3 whites out of 10 total balls makes P(white) = 3/10
November 10, 2014

Calculus
Not sure why there are two = signs. Also, Phi is usually an angle, unless it is the golden ratio. I've never seen either one raised to such a power. Where did you get the "equation"?
November 10, 2014

algebra
both domain and range are (-∞,+∞) the domain for all polynomials is the same.
November 10, 2014

Calculus
so, why toss in the product rule as well? :-)
November 10, 2014

calc/trig
to find θ, note that tanθ = 84/130
November 10, 2014

trig
cosθ = 1/9 θ = 83.6° That is your reference angle. Since cosine is positive in QI and QIV, your two angles are 83.6° and (360-83.6)°
November 10, 2014

Math
(6 1/2)/(5 1/5) = (13/2)/(26/5) = 13/2 * 5/26 = (13*5)/(2*26) = 5/4 = 1 1/4
November 10, 2014

science
s = 1/2 at^2 v = at = √(2as) So, just plug in the numbers to get v.
November 10, 2014

algebra
Note that A(8,12)+(-5,-13) = M(3,-1) Since M is halfway to B, we need to add the same amounts to M that got us there from A: M(3,-1)+(-5,-13) = B(-2,-14)
November 10, 2014

Math please help
Just so you can check your work, you should come up with 1/8
November 10, 2014

math
5.6930 x 10^4
November 10, 2014

pre calc
f(x) = 6x^7 + 7x^6 f'(x) = 42x^6 + 42x^5 = 42x^5(x+1) so, now it's easy to see where f'(x) = 0
November 10, 2014

Math Pre Calc Help
(cos^4x -sin ^4 x)/(sin^2x) (cos^2x-sin^2x)(cos^2x+sin^2x)/sin^2x (cos^2x-sin^2x)(1)/sin^2x cos^2x/sin^2x - sin^2x/sin^2x cot^2x - 1
November 10, 2014

College Math
v0 t - 16t^2 = 0 when t=8, so 8 v0 - 1024 = 0 v0 = 128 Now just find the vertex of the parabola, at t = -b/2a which in this case is at t = v0/32 = 4 that sounds correct, since it is at half the time to hit. 4 sec up, 4 sec down. So, just find s(4)
November 10, 2014

Pre-Calc/Trig
y-intercept is where x=0: f(0) = 0 x-intercept is where y=0 y = x(4-x^2) = x(2-x)(2+x) So, the x-intercepts are at -2,0,+2
November 10, 2014

Math 201 ( Algebra)
If there are x at $40 and y at $80, then 40x+80y = 1000 x = y+80 Now just solve for x and y
November 10, 2014

calculus
if the square has side s and the circle has radius r, then r+s = 360 pi r^2 = (360-r)^2 (pi-1)r^2 + 720r - 129600 = 0 r = 129.85 ...
November 10, 2014

Calculus
y = x^(2/3) * ((5/2)-(x) y' = (2/3)x^(-1/3)*(5/2 - x) + x^(2/3)(-1) = 5(1-x) / (3*x^(1/3)) So, y'=0 when x=1 y" = -5(2x+1) / (9x^(4/3)) y"(1) < 0, so f(1) is a maximum See the graph at http://www.wolframalpha.com/input/?i=+%28x^2%29^%281%2F3%29+*+%28%285%...
November 10, 2014

Calculus angle of elevation with elevator
The two solutions below have exactly the same problem, and each step is shown. Where do you get stuck?
November 10, 2014

Calculus angle of elevation with elevator
see the related questions below - just change the numbers
November 10, 2014

limerick poem
oops - bad closing tag...
November 10, 2014

limerick poem
Just because it has five lines and rhymes, that does not make it a limerick. There is a certain very strict meter which must be followed. Read a bunch of them, then try again. Your meter is way off. The rhythm must be as in There was an old man from Nantucket Who kept all his ...
November 10, 2014

Math! Algebra 1!
If the still-water speed is s, then since distance = speed*time, then in equal time (say, t=1), (s+1.5) = 2(s-1.5) s+1.5 = 2s-3 s = 4.5 100/4.5 = 22.22 hrs or 22 hr 13 min 20 sec
November 10, 2014

Calculus angle of elevation
of course there is... when the elevator is x meters up, tanθ = (x-31)/22 So, sec^2θ dθ/dt = 1/22 dx/dt when x=20, tanθ = -11/22, so sec^2θ = 5/4 5/4 dθ/dt = 1/22 (3) dθ/dt = 55/6 m/s Is one of the steps unclear?
November 10, 2014

Calculus angle of elevation
see the related questions below. The first is the identical problem -- just change the numbers.
November 10, 2014

math
so, OHE = 3HER Sure you didn't leave something out?
November 10, 2014

mathematics
2OR = 2x+5 2OR = HE+5 HE = 2OR-5
November 10, 2014

mathematics - incomplete
can you not tell there is some missing information here?
November 10, 2014

Science
(8m/s)/(3s) = 8/3 m/s^2 (40m/s)/(8s) = 5 m/s^2 which is greater?
November 10, 2014

Algebra
the factors of -7 are -1 and 7 1 and -7 can you pick them so they add up to -6? (x+1)(x-7)
November 10, 2014

math
So, you must want the pair (cosθ,sinθ) which is the point on the unit circle associated with θ. 30: (0.866,0.5) 60: (0.5,0.866)
November 10, 2014

math
ok - I thought that might be it. So, now, what ordered pair did you have in mind? 30 degrees is just an angle. Is there supposed to be an ordered pair associated with an angle?
November 10, 2014

math
eh? Not sure what it is you are asking. ff?
November 10, 2014

geometry - incomplete
so, what is the question, again? You seem to have dropped some data, as well as what it is you are asking.
November 10, 2014

math
just write the data as given: a+b+c+d = 9000 a+c+d = 4b b+d = 4/5 (a+c) The first says that a+c+d = 9000-b using the second, that means that 9000-b = 4b b = 1800 So, now we have a+c+d = 7200 1800+d = 4/5 (a+c) Now we know that a+d = 7200-d, so 1800+d = 4/5 (7200-d) 1800+d = ...
November 10, 2014

math(fractions)
no idea. How long is the Blue Trail?
November 10, 2014

calculus
online, we generally use ^ for powers, and * for multiplication. Why bother changing the way it was posted? And the quotient rule says 5(3x+4)^4(3)(4x+1)^2 - (3x+4)^5(2(4x+1)(4)) ----------------------------------------- (4x+1)^4 (3x+4)^4 (15(4x+1)-8(3x+4...
November 10, 2014

what is the rate of change of the angle of eleva
see related questions below
November 10, 2014

calculus
when the elevator is x meters up, tanθ = (x-20)/20 So, sec^2θ dθ/dt = 1/10 dx/dt when x=10, tanθ = -1/2, so sec^2θ = 5/4 5/4 dθ/dt = 1/10 (5) dθ/dt = 2/5 m/s
November 9, 2014

physics
Look out below!! Was there a question in there somewhere?
November 9, 2014

phyics
If the tug pulls at speed v on a course of θ, then in x-y coordinates, 15 + 9cos60° + 35 sinθ = 0 19.5 + 35 sinθ = 0 sinθ = -0.5571 θ = N 33.9° W Now you can figure part B.
November 9, 2014

Calculus
revenue = price * quantity, so r = x(160-2x) = 160x - 2x^2 max revenue when r'=0, or x = 40 So, just plug that in as needed.
November 9, 2014

Math 112
not so. The value is a non-terminating decimal, so it cannot be written exactly. The calculator just shows the first few digits. The only way to write it exactly is: √3
November 9, 2014

math
14.1√2 = ?
November 9, 2014

College Algebra
27.95 + 0.15m = 45.95 find m
November 9, 2014

Math
how much in taxes? well, duh: 7% .07 * 43.99 = $3.08 so, add the price to the taxes to get the total
November 9, 2014

Algebra
If you mean 2/3y + 5 - 3 - 11/12y then collect like terms: 2/3 y - 11/12 y + 5-3 (2/3 - 11/12)y + 2 (8/12 - 11/12)y + 2 (-3/12)y + 2 -1/4 y + 2
November 9, 2014

ap calc
so, solve the equation for f'. You have 3sinx = -2cosx tanx = -2/3 So, that gives you x for maximum value of f(x). Just plug it in and evaluate f(x). Of course, you need to recall how to take sin(arctan(x)) and cos(arctan(x)) But that's just trig, right? Or, note that ...
November 9, 2014

Can you check my answer - Physics
clearly the net force is the sum of the downward and upward forces: -1.5N + 0.7N = -0.8N That is, 0.8N downward You just added the magnitudes, but did not take into account the directions
November 9, 2014

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