Saturday
April 19, 2014

Posts by Steve


Total # Posts: 21,782

math
x + x+10 = 90 just solve for x

math
add up the amount of copper in each part. It must total the amount of copper in the final alloy .10*25 + .18x = .13(25+x) now just solve for x

math
how many ways can you choose 3 dishes from a menu of 8? my answer is 56

Math
√(x+2) = x x+2 = x^2 x^2-x-2 = 0 (x-2)(x+1) = 0 x = 2 or -1 Now just plug in the roots. -1 does not fit because √1 = 1, not -1. -1 is the solution to -√(x+2)=x because both the plus and minus roots when squared come out positive.

Math
since each dimension is 1/3 as big, the volume (product of all three dimensions) is 1/27 as much.

math
y = (cos 2x)^x log y = x log(cos 2x) 1/y y' = log(cos 2x) + x/cos2x (-2sin2x) y' = (cos2x)^x (log cos2x - 2x*tan2x) It is interesting to note that if y = u^v y' = vu^(v-1) u' + (logv)(u^v)(v') If v is a constant, v'=0, so we have the familiar power rule...

Pre calculus
thx

Pre calculus
Can you show me the steps or is this just on calculator?

Pre calculus
sorry it was f(x)= not (-) I got no real roots either

Pre calculus
Assuming you meant that - sign at the front, -x^3+2x^2-15x+30 = -x^2(x-2) -15(x-2) = -(x-2)(x^2+15) If you did mean x^3+2x^2-15x+30 then there are no rational roots, and you have to fall back on numerical methods, like bisection or Horner's method.

Pre calculus
Find all roots f(x)- x^3+2x^2-15x+30 Factor f(x) completely. I can't find any roots and always get a remainder with 1, -1, 2, -2 What do you do if you cannot find a root?? Using Calc button on ti84 I got X= -5.619 Y=1.4E-11 Still can't find zeros...

math
y = vt - 4.9t^2 max height h is at t = v/9.8, so h = v^2/19.6 v^2 = 50*19.6 v = 31.3 m/s

physical science
Provide three statements that demonstrate the importance of units when describing motion.

maths
since 7 = √49, log497 = 1/2

math
you know that ∫ e^u du = e^u so, let u = sec(2x) now you're almost there.

Math
i) no ii) no iii) yes, as always

Math
no,no,yes

maths
s = pi r(r+s) now plug and chug

mathematics
.05x + .04(280-x) = 12.80 now just solve for x

math
x + x+30 = 90

physics
you need v such that 3i + 4j + 2(xi+yj) = 0 3+2x = 0 4+2y = 0 v = -3/2 i -2j now just get the magnitude and direction.

Algebra
(f+g)(x) = f(x) + g(x) so, just plug in the value for f and g.

Calculus Help Please!!!
remember: wolframalpha is your friend!

Calculus Help Please!!!
just follow the theorem. f(0) = 1 f(2) = -1 so, the average slope on the interval is (-1-1)/(2-0) = -1 So, now we need to find c such that f'(c) = -1 f'(x) = 4x-5 so, where does 4x-5 = -1? x = 1 1 is inside [0,2], as predicted by the Theorem. In fact, since f(1) = -2, ...

Calculus Help
That's what I get. It seems we agree. Is there a chance the answer key is in error? Maybe Reiny or Damon can see an error.

Calculus Help
v = k(r0-r)r^2 = kr0*r^2 - kr^3 dv/dr = 2kr0*r - 3kr^2 = kr(2r0 - 3r) so, v obtains a max at r = 2/3 r0 what about the ends of the interval? v(1/2 r0) = k(1/2 r0)(1/4 r0^2) = k/8 r0^3 v(2/3 r0) = k(1/3 r0)(4/9 r0^2) = 4k/27 r0^3 v(r0) = 0 so, since 4/27 > 1/8 max v = 4k/27 ...

Calculas
the marginal profit is dP/dx = 100 - 6x lnx - 3x so, now plug in x=4

science
which of the following examples does not demonstrate a change in velocity? an elevator coming to a stop as it reaches the top floor a cruise ship heading west at a constant speed a soccer ball passed across the field a train remains at a constant speed as it goes around a bend...

physical science
Which of the following pairs of objects would have the strongest gravitational pull? two buildings in the same city ← two tall buildings in different cities two stars very far away from each other two stars very close to each other my answer is c

science
Which of the following pairs of objects would have the strongest gravitational pull? two buildings in the same city ← two tall buildings in different cities two stars very far away from each other two stars very close to each other my answer is c

science
Which of the following examples does not demonstrate a change in velocity? An elevator slows down in order to stop at the top floor ← A cruise ship travels west at a constant speed A soccer ball is passed across the field or ← A train remains at a constant speed a...

alg
If you mean (u-2)/(u-4) + 6 = u + (u-6)/(4-u) multiply by u-4 to clear the fractions: (u-2) + 6(u-4) = u(u-4) - (u-6) u-2+6u-24 = u^2-4u-u+6 u^2 - 12u + 32 = 0 (u-4)(u-8) = 0 u = 4 or 8 But, u=4 is not allowed, because the original equation divided by (u-4). So, the only solut...

algebra
(2/3k)+(k/k+1) = (3k^2+2k+2)/(3k(k+1)) (k/k+1) -(3/k) = (k^2-3k-3)/(k(k+1)) divide the two and you have (3k^2+2k+2) / 3(k^2-3k-3)

physical science
would 2 stars very far away from each other have a strong gravitational pull

physical science
is an elevator slowing down as it reaches the top floor a change in velocity?

ALG
do you mean 1/r = 1/r1 + 1/r2 ? If so, 1/r2 = 1/r - 1/r1 = (r1-r)/(r*r1) so, r2 = r*r1/(r1-r)

Math, Geomertry
given the distance between centers, the distance from the center of the moon to the surface of the earth is 248740 miles. The distance from the center of the sun to the center of the moon is thus 93000000-248740 = 92751260 miles. At that distance, the moon casts a shadow (umbr...

alg
twice the distance means 1/4 the loudness

alg
mosey on over to calc101.com and click on the "long division" link. You can play around with polynomial division and see all the details.

MATH
16 = 128/8 3 5/8 = 29/8 128-29 = 99 ...

Algebra
x^2 - 7x - 4 x^2 - 7x + (7/2)^2 - 4 - (7/2)^2 (x - 7/2)^2 - 65/4 y=0 when x - 7/2 = ±√65/2 x = (7±√65)/2 x = 7.53 or -.53

Algebra
rock hits ground when y=0, so -0.02x^2 + 0.8x + 37 = 0 x = 67.43

Algebra - help
I get 160.56 just use the quadratic formula. x = (-9.6 ±√(9.6^2 + 4(.06)(5.4)))/-.12 = (-9.6 ±√93.456)/-.12 = (-9.6 ±9.667)/-.12 = .067/-.12 or 19.267/.12 = -0.558 or 160.56 If you had plugged in bobpursley's data, you'd have seen that ...

Calculus
yes, that would be the asymptotic curve.

science
what doesn't have to be measured in order to describe motion

science
what type of friction does a maglev train reduce

geometry
3/4 * 100*32*8 ft^3

science
When a basketball changes shape as it bounces off the floor is it because of balanced force acting on it?

physical science
a model train moving at a constant speed around a circular track has a constant velocity?

MATH
810/1080 * 4 = 3 years 4/3 as many boys, 3/4 as many years

math
convert all to decimal, then it's easy 0.25 = 0.25 1/3 = 0.33 3/4 = 0.75 49% = 0.49

Maths
I assume you're looking for a and d, eh? a+6d = 2(a+2d) (4/2)(2a+3d) = 42 Now just solve for a and d.

maths
dx = 5 dt dy = -3 dt dz = 4 dt ds = √((dx)^2 + (dy)^2 + (dz)^2) plug in the values and integrate. (fix the typos first, though)

math
you've posted a bunch of these basic interest problems, and had them done for you. How about showing us what you've learned?

Calculus
Since f(2) = -21, f^-1(-21) = 2 f'(x) = -6x^2-3 (f^-1)'(-21) = 1/f'(f^-1(-21)) = 1/f'(2) = -1/27

science
When the car begins to stop, your body tends to stay in motion until acted upon by an outside force. In a fraction of a second, that outside force is exerted by your seat belt, or the windshield, which then slows you down. Quickly.

algebra
almost always you can take "of" to mean "times" 25% of 200 = .25 * 200 = 50

percentages/word problem
(1-.30)p 72.09 p = 72.09/.70 = 102.98

physical science
If You Were Riding A Train List Some Examples Of Items That Would Make It Seem Like You Weren't Moving

math
looks like there was a 20% discount, plus 6% tax.

Math
Note that 4x^2 and 9 are both perfect squares, so the first thing I'd try is (2x+3)^2 good guess!

Math - Int Trig
I'll do one. Do the others in like wise. If you get stuck, come on back with what you did. (g∘h) = 3/(h^2+2) = 3/(x-2+2) = 3/x (g∘h)(-2) = 3/-2 = -3/2 The domain of h is x>=2 The domain of g is all reals, since x^2+2 is never zero. So, the domain of (g∘...

Algebra
the common denominator is (b+1)(b+2)(b-2), so when you place all over the common denominator, you have [4(b^2-4) + 1(b+1) + 5(b+1)(b-2)]/[(b+1)(b^2-4)] (9b^2-4b-25)/(b^3+b^2-4b-4)

PRE CALC
cos k*pi = 1,-1,1,-1 so they add to zero and the sum is just 4

Algebra
(x^3)^-4 = x^-12 (-2x^-2)^-3 = (-2)^-3 (x^-2)^-3 = -1/8 x^6 multiply those and you have -1/8 x^-6 = -1/(8x^6)

Math
so, what's the problem? 2 2*159 = 318 3 ... 5 10

math - 6th grade
subtract 3x+2 from both sides and you have 4x+2 -3x-2 = 3x+9 -3x-2 x = 7

Math
Tn = -3n

Math
subtract 3 for each successive term. So, by the 93rd term, you have done it 92 times. -3 - 3*92 = -279

Math
I don't see any equations (gotta have an = sign for that) add 4 for each term. So, for the 76th term, you have added 4 75 times, and it is thus -2 + 75*4 = 298

Geometry
Each lateral face is a rectangle. The trapezoid has four sides, possibly all different, so you have four rectangles. Then add the areas of the two trapezoidal bases.

Geometry
well, duh - it's the area of the triangular base. If you're discussing prisms, you've surely already covered triangles, no?

Math
looks like y = 2 - x/2 Note that y decreases by 1 when x increases by 2, making the slope -1/2

math
subtract the smaller rectangle from the larger. The remainder is the area covered by the frame. 28*24 - 24*20 = ? or, rewriting things a bit, 28*24 - 20*24 = 8*24 = ?

math
If you look at the table, you should find a value of 1500(1+.12/4)^(4*8) = 3862.62

math
3500((1+.12/4)^4 - 1) = 439.28

geometry maths
well, of course, the larger circle has radius 1. Draw a diagram of the upper right quarter of the square. Include half the diagonal of the square, which goes through the centers of the two circles (O and Q), which are tangent at point P. Draw a vertical diameter of the smaller...

Calculus
20^n = 5^n * 4^n so, you have 5^n/20^n + 4^n/20^n = 1/4^n + 1/5^n both of which converge

Calculus
sure you do. It's just a geometric series a = 1/e^2 r = 1/e^2 S = a/1-r = (1/e^2)/(1 - 1/e^2) = 1/(e^2-1)

Algebra 2
division by zero is not defined. So, when the denominator is zero, f(x) is not defined. x^2-4x+3 = (x-1)(x-3) so, when x=1 or 3, you are trying to divide by zero. Those values are not part of the domain. Note that x^2-9 = (x-3)(x+3) So, for any value except x=3, f(x) = (x+3)/(...

Math
just determine how long each call was, then add them up. 10:15-11:00 = 45 minutes 12:30-1:15 = 45 minutes total = 90 minutes

math
2 1/4 + 1 1/2 = 3 3/4

Math
240*8*40 = 76800 just divide 8,000,000 by that

Maths please someone help me out!!!
.2^(t/4) multiplies by 0.2 every time t increases by 4. That's how the efficiency is described in words. so, get out your calculator (online or physical) and evaluate some values for t. As a sanity check, 50% is a little more than twice as much as 20%, so expect t to be so...

geometry - eh?
a circle has only a radius, not an inradius and a circumradius.

maths
have you a calculator? Just punch in the numbers.

geometry - wow
heck, I don't even have a diagram!

maths
a^2 + b^2 = 16 2ab = 7 (a-b)^2 = 16-7 a-b = ±3

mathematics
3x^2+6x-2 = 0 better use the quadratic formula. x = (-6±√60)/6

mathematics - eh?
gotta clean up those ? marks with + or - signs.

Algebra
e^2-e-12 = (e-4)(e+3) dividing by e-4 leaves e+3 similarly, a^2+11a+30 = (a+5)(a+6) x^2+3x+2 = (x+1)(x+2) x^2+5x+6 = (x+2)(x+3) now the LCM should be easy

Maths
84+65+76 = 225 to have an 80 average of 4 tests he needs 320 total points. good luck, Jim.

High school math
last I checked, 2+2=4

High school math
I assume you're just making a test post...

math
depends on the shape. Unless the base is square, there's no way to find the other two missing values.

geometry
I'd say it's h 487 = 25/3 pi h

Algebra
heck, the answer to the 2nd part provides the answer to the first part: x y ∆y 1 3 2 10 7 3 29 19 4 66 37 5 127 61 6 218 91 as you can see, x has to increase less and less for y to double.

Algebra - bizarre
now this is getting weird. Another person assuming that sqrt(...) is the exact notation? Go ask the person who gave you this, to show you the solution we already posted.

Calculus
dy/dx

Calculus - oops
rats - that's dx/dt = -6csc^2θ dθ/dt when θ=π/3, we have x = 6/√3 and cscθ = 2/√ dx/dt = -6(4/3)(-π/3) = 8π/3 km/min

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