Sunday
February 7, 2016

Posts by steve

Total # Posts: 37,440

math
good -- now you can work on your spelling...
November 28, 2015

Math
L{e^at f(t)} = F(s-a) so, L{e^4t f(t)} = F(s-4) now, what is L^-1(1/s^3) ?
November 28, 2015

Math
cos = 1/sec
November 28, 2015

Algebra
17n+11 - (5n+6) - (4n+5)
November 28, 2015

Algebra 2
b+m+p+n=17 200b+225m+175p+150n=3400 m = b+p+n-1 p = 2n Now just solve for the 4 unknowns.
November 28, 2015

maths
6200*.09*2.75
November 28, 2015

Solving Trig Equations
as you say, sinx = ±√3/2 You know the reference angle is π/3. sinx > 0 in QI, QII, so you have π/3 and 2π/3 sinx < 0 in QIII, QIV, so that gives you 4π/3 and 5π/3 But, for this problem, the domain is [-π,0] (QIII and QIV), so ...
November 27, 2015

math
scaling preserves angles, so all three triangles are similar.
November 27, 2015

math
S5 = 5/2 (2a+4d) S2 = 2/2 (2a+d) The sum of the last 3 is S5-S2, so we have S2 = 55-48 = 7 = 2a+d 2a+d = 7 5/2 (2a+4d) = 55 a=1, d=5 So, S3 = 3/2 (2+2*5) = 18
November 27, 2015

Math
the circumference is 8π ft. 2 ft per flower means you get 8π/2 = 4π ≈ 12 plants 20 seeds @ 2 ft/seed means a circle with a 40 ft circumference. So, the diameter is 40/π ≈ 12.75 ft
November 27, 2015

Mathematics
what is the formula for the ith term again? It seems garbled. There's a (3/n * floating around.
November 27, 2015

Math
y-intercept is where x=0. avg rate is (56-52)/(3-1) Looks like that would be 2 more hours. So, {0..5}
November 27, 2015

Math (prob)
the experimental results are his pass/fail of the test.
November 27, 2015

Calculus
let u = (x-r)^2 du = 2(x-r) dx dv = (1/r) e^(-x/r) dx v = e^(-x/r) ∫ u dv = uv - ∫ v du = (x-r)^2 e^(-x/r) - 2∫(x-r) e^(-x/r) dx Now do it all over again. Notice that the power of (x-r) has been reduced by one.
November 27, 2015

math
rotation of any multiple of 360/8 = 45 degrees. Also, a reflection across any of its 8 lines of symmetry.
November 27, 2015

Math
T(x) = 45 - x/300 (300,1) is not a point on the line. x has to increase by 300 for T to drop by 1°. Thus, (300,44) is the point you are after.
November 27, 2015

math
If there are x large prints, then there are 2x small prints. To break even, he needs 20*2x + 45*x = 510 I think you can now easily answer all the questions. Most of them don't even depend on the number of prints sold.
November 27, 2015

math
(A): the circle has a circumference of 8π feet. If the seeds are at least 2 ft apart, then at most 8π/2 = 4π ≈ 12 seeds may be planted.
November 27, 2015

trigonometry
since X is the foot of the altitude, any triangle with X as an angle will be a right triangle.
November 27, 2015

trigonometry
3-sided
November 27, 2015

Trigonometry URGENT!
amplitude is half the distance between the extremes. In this case, (125-99)/2 = 13 The midline (where sin(x) = 0) is (125+99)/2 = 112 The period is twice the time from max to min, or 28*2 = 56 So, we're looking at something like y=13 sin(pi/28 t)+112 Now for the phase ...
November 27, 2015

Tamae
220 * .05 = ?
November 27, 2015

Math calculus
see related questions below
November 27, 2015

Integral Calculus
if you set u = arctan(x), you have u du I expect you can handle that...
November 27, 2015

jabu
100 km/hr = 27.78 m/s v = √(2as) 27.78 = √(100a) a = 7.716 m/s^2 That is the minimum acceleration which will do the job. There is no maximum value.
November 27, 2015

Math
If the markup is x%, then (1+x/100)*.84 = 1.12 x = 33.33% = 1/3 1200 * 4/3 = 1600 check: 1600*.84 = 1344 = 1200*1.12
November 27, 2015

Precalculus ????
23 is the maximum hours, but you want the maximum temperature. sin(x) has a maximum of 1 5sin(x) has a max of 5 5sin(x)+19 has a max of 24 It appears there is a typo, since 24 is not a choice.
November 27, 2015

math
You have 1-2 + 3-4 + ... + 99-100 = (-1) + (-1) + (-1) ... + (-1) (50 times) = -50 Naturally, the 2nd sum is then +50
November 27, 2015

math
one step at a time... 11/15=(1/a+(b/c+(d/e+f))) 11 = 15(1/a+(b/c+(d/e+f))) 11 = 15/a + 15(b/c+(d/e+f)) 15/a = 11 - 15(b/c+(d/e+f)) a = 15/(11 - 15(b/c+(d/e+f))) Now for b: 11 = 15/a + 15(b/c+(d/e+f)) 15(b/c+(d/e+f)) = 11 - 15/a (b/c+(d/e+f)) = 11/15 - 1/a b/c = 11/15 - 1/a - (...
November 27, 2015

math
If there are n survivors, there are 5n meals. After 2 days, 2n meals have been eaten, leaving 3n Then the 3n meals lasted the n-4 survivors 5 days: 3n/(n-4) = 5 Now just find n
November 27, 2015

math
list the powers of 2 and their remainders: 2^1 2 2^2 4 2^3 1 2^4 2 2^5 4 2^6 1 ... you can see a pattern. So see how many times the pattern is repeated in 1000 powers of 2, and how many powers are left over.
November 27, 2015

Precalculus
no ideas of your own to provide? These two problems are really the same thing with different numbers. As you might imagine, the trick is to come up with a function you can analyze. So, on the first one, if we are starting at the midline, then since sin(0) = 0, we expect to ...
November 26, 2015

Math - PS
skip that middle section. It was a blind alley I forgot to erase. Cool problem. I had to try several things before I hit on the right trick to convert all the sums to products.
November 26, 2015

Math
sin2x+cos2x = √2(sin2x * 1/√2 + cos2x * 1/√2) = √2sin(2x+π/4) so you have [√2sin(2x+π/4)+1]/[√2sin(2x+π/4)-1] = [√2sin(2x+π/4)+1]^2/(2sin^2(2x+π/4)-1) Now, using sum-to-product formulas, √2sinu+1 = √...
November 26, 2015

maths.augusco
1/5 : 3/10 : 7/1 = 2/10 : 3/10 : 70/10 = 2:3:70 There will be some pieces in the mix, as 75 does not divide 720 I suspect a typo. Fix it, and you will see a better division of apples.
November 26, 2015

discriminant
24
November 26, 2015

c programming
what is the difficulty? Do you have trouble with I/O? Don't understand arrays? Don't understand functions? Have you worked out pseudo-code that takes the necessary steps?
November 26, 2015

Programming
well, just follow the loop. On entry, count=1 next iteration: count steps up by 2, so count=3 next iteration: count=5, so exit so, the output is 1 3
November 26, 2015

Pre Calculas
In fact, ln56/ln7 = log756
November 26, 2015

math
true
November 26, 2015

calculus
The first step is just to expand the polynomial: e^2t + 2 + e^-2t Now integrate each term. Or, remember that your function is just (2 cosh t)^2 = 4cosh^2(t) now use the half-angle formula for hyperbolic functions, and you will get the same answer. Hmm. I guess just expanding ...
November 25, 2015

math
since time = distance/speed, 4/(x-2) = 12/(x+2) Now just find x.
November 25, 2015

math
see related questions below.
November 25, 2015

maths
1/3 * 3/4 (1 is not prime)
November 25, 2015

Algebra
the growth after t hours is 1.036^t so, find t where 1.036^t = 2 t log1.036 = log2 t = log2/log1.036 = 19.5986
November 25, 2015

Geometry
If the answer was (2,5), the line of reflection was y=4. That, or A=(-3,-3)
November 25, 2015

Geometry
(-3,3) -> (2,3) -> (2,-1) or, (-3,3) -> (-3,-1) -> (2,-1) typo?
November 25, 2015

Algebra
exclude values where the denominator is zero. So, where is (k+7) = 0?
November 25, 2015

math
-sin10°
November 25, 2015

just checking(:
Bzzt. But thanks for playing It is b) -2 -4y = 8x y = (8/-4)x = -2x
November 25, 2015

Algebra 1 Honors
2.50 + 0.35(15.75-1)*4 = $23.15
November 25, 2015

math
it occurs where d/dx(R-C) = 0 I get a maximum profit of 3992.81 at x=2875
November 25, 2015

Trig
This is not an identity. It is an equation to solve. cos 2x = -.3 cos 72.5° = 0.3 But, we have -.3, so 2x is in QII or QIII 2x = 107.5° or 255.5° x = 53.75° or 127.75° You can also add 180° to each of those, since cos(2x) has period of pi. That will ...
November 25, 2015

math
clearly, y=x
November 25, 2015

science
what is the speed of sound at 25°C? If that speed is s, then If the cliff has height, it hits the bottom at time t, where 4.9t^2 = h. So, h = (8-√(h/4.9))*s Plug in your speed s, and find h.
November 25, 2015

math - eh?
Better read your question. It is gibberish.
November 25, 2015

math
18 * (32/72) 30 * (8/12)
November 25, 2015

Math
true, false if x has powers, it is a polynomial. If x is the power, it is an exponential, as in e^x polynomials have constant powers of a variable. exponentials have variable powers of a constant.
November 25, 2015

Pre Calculus
for any positive real a, y = a^x always goes through (0,1), so y = 4a^x always goes through (0,4) y = a^x + 3 also goes through there. y = h*a^x + k too, if h+k=4 negative powers also work.
November 25, 2015

Algebra
If x hours at 57 mi/hr, then since distance = speed * time, 57x + 56(4.5-x) = 254
November 25, 2015

Geometry
yes.
November 25, 2015

Calculus 1
You can see a nice graph with grid lines here: http://rechneronline.de/function-graphs/ You may have to adjust the y scale some so it fits. You can use that to estimate the area. I'm sure you can then evaluate the integral.
November 25, 2015

derivatives
is that (cos t)^2 or cos(t^2) ? Then express t as functions of x and y, and you have dy/dx = (dt/dx) / (dt/dy) then you can use that to get the 2nd derivative
November 25, 2015

electron theory and ohms law
ummm. E = IR ? This time find I.
November 25, 2015

electron theory and ohms law
E = IR = 6.4 * 20
November 25, 2015

math
average cost is (1/3 x^3 – 18x^2 + 160x)/x = 1/3 x^2 - 18x + 160 marginal cost is x^2-26x+160 so, where is 1/3 x^2 - 18x = x^2 - 26x ?
November 25, 2015

Algebra II, part 2
#6. Surely by now you can do this... #7. b^2-4ac = 9+4*2*18 #8. 3√-3 = 3√3 i #9. Multiply top and bottom by conjugate: 8(3-2i)/13
November 24, 2015

Algebra II
#1. x^2 has negative coefficient. downward #2. (5/2)^2 #3. hint: 15+1 = 16 #4. does not factor. Did you mean +2x? #5. shift left 2, scale vertically by 1/3, shift up 5
November 24, 2015

algebra 2
Well, I see 2x^2+3x+1 and 3ay^2+9a If you want to factor them, then you have (2x+1)(x+1) and 3a(y^2+3) Other than that, I'm not sure what you want to do with them.
November 24, 2015

Trigonometry
#1. no calculator? It will be in 1st quadrant. #2. how long is the court? The angle is x where tan(x) = 2.44/(court length)
November 24, 2015

Math
so, if the width is w, 2(w + 2w) = 126
November 24, 2015

Algebra 2
y = (x-10)(x-4) I expect you can take it from there, no?
November 24, 2015

Math
yep.
November 24, 2015

Math
the range is the set of 2nd elements of the pairs.
November 24, 2015

Calculus III
Looks ok to me
November 24, 2015

Physics
F = ma = 80kg * 9.8 m/s^2 W = Fd = F * 6m P = W/s = W / 15s P = 80*9.8*6/15 = 313.6 W Now you can figure the % eff.
November 24, 2015

MacArthur physics
height: s = 4.9t^2 speed: 9.8t range: 20t
November 24, 2015

Math
cool. nice and wavy.
November 24, 2015

arvind mahila college
T7/T4 = r^3 = (8/9)/3 = 8/27 so, r = 2/3 Now you can find the 1st term and thus whatever terms you want.
November 24, 2015

Algebra
Been there, done that. http://www.jiskha.com/display.cgi?id=1448344846
November 24, 2015

Math
well, what is 3 cows plus 6 cows? 3 doughnuts plus 3 doughnuts? whatever x is, you have 3+3 of it.
November 24, 2015

math
c(x) = 3 + x/3000 + e^(-.003x) c'(x) = 1/3000 - .003e^(-.003x) So, you can see that the cost to produce a unit consists of a fixed amount, plus a steadily decreasing variable amount as more are produced. That means that the cost of the 100th unit is c'(100) = 1/3000...
November 24, 2015

Algebra 1
without knowing step 4, it's hard to say. Both distributive and associative properties are expressed. I doubt very much that it is a fact, as it's just an expression, with no assertion that it is true.
November 24, 2015

Math,Mensuration
just plug in your numbers: S = 2πr(r+h) V = πr^2 h
November 24, 2015

math
If the length is x, then the width is x-4. So, the perimeter is 2(x + x-4) = 56
November 24, 2015

college algebra
Assuming you meant a bicycle tire makes 3 complete revolutions for each revolution of the pedal then we have (in inches/minute) 100 * 3 * 27π Now just convert that to miles/hour.
November 24, 2015

math
base = s/2 leg = 2s s/2 + 2*2s + 4s = 34 Now solve for s, and then the triangle's sides.
November 24, 2015

Algebra
since time = distance/speed, 20/(x-3) + 20/(x+3) = 5
November 24, 2015

Algebra
just solve t^2-2t = 48 t^2-2t-48 = 0 (t-8)(t+6) = 0 I expect you can take it from there, no?
November 24, 2015

Math
multiply by -3
November 24, 2015

math
review the definition of cot(x). You will see that if the height is h, h*cot27° - h*cot29° = 1000
November 24, 2015

Maths
x+y = 32 4x-5 = 8y Solve for x and y, then x-y
November 24, 2015

Algebra
If x at 5%, y at 10%, then 200+x+y at 15% x+y+200+x+y = 7000 .05x + .10y + .15(200+x+y) = 815 Now just solve for x and y, and then x+y+200
November 24, 2015

math (check answers)
looks good to me. nice work.
November 24, 2015

math
so, do you mean ln(xy-sqrt(x^2-y^2)) or ln(xy)-sqrt(x^2-y^2) I will assume the first, since the 2nd is much easier ∂z/∂x = 1/ln(xy-√(x^2-y^2)) * (y-x/√(x^2-y^2)) and similarly for y.
November 23, 2015

math
you can use the techniques discussed here http://math.stackexchange.com/questions/783469/evaluate-the-limit-with-taylor-series to break it into pieces, and use the Taylor series to evaluate using the linearity of limits. Each function involved has a relatively easy-to-get series.
November 23, 2015

Physics
(30 m/s)/(5s) = 30/5 = 6 m/s^2
November 23, 2015

Physics
(25-15) m/s ------------------ = 2 s 5 m/s^2
November 23, 2015

TECH MATH
the volume of a cylindrical hole in a sphere is discussed here: http://mathworld.wolfram.com/SphericalRing.html Just plug in your numbers.
November 23, 2015

math
since 9=3^2, log_3(9^12) = log_3(3^24) = 24 Not quite sure what 9logexponent 12 means.
November 23, 2015

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