Thursday
November 27, 2014

Posts by STEVE


Total # Posts: 27,032

math
Since when do Alonso and Italian chicken sound Chinese? and that's "whoever deciphers this." The phrase acts as the object of the preposition, not just "who".
October 27, 2014

Calculus
from you formula for v, dv/dt = 4pi r^2 dr/dt now plug in the numbers.
October 26, 2014

Calculus
I think you have a typo. I'm sure you meant y = 2sinx + (sinx)^2 since y(π/6) = 2(1/2) + 1/4 = 5/4 So, y' = 2cosx + 2 sinx cosx at x=π/6, y' = 2(√3/2) + 2(1/2)(√3/2) = √3 + √3/2 = 3√3/2 Now you have a point and a slope. Dig ...
October 26, 2014

Fractions
Starting with x peaches, a = x-(x/2 + 1/2) b = a - (a/3 + 1/3) c = b - (b/4 + 3/4) c - (c/5 + 1/5) = 19 now start substituting in and you wind up with x = 101
October 26, 2014

Calculus
f'(x) = -4x-2 f'(-1) = 2 point-slope form: y+2 = 2(x+1)
October 26, 2014

Calculas
y = secx y = (cosx)^-1 y' = -1 (cosx)^-2 (-sinx) = sinx/cos^2x = secx tanx similarly for tanx, using the quotient rule
October 26, 2014

calculus
a square has minimum perimeter for a given area
October 26, 2014

Algebra
it's easiest to use the polar form if z = r cisθ z^2 = r^2 cis2θ so, r^2 cis2θ = 2 cis π/2 r = ±√2 θ = π/4 So, we have √2 cis π/4 -√2 cis π/4 √2/√2 + √2/√2 i = 1+i or -(1+i) check: (1+...
October 26, 2014

Algebra
That vertical asymptote at x = -1 means the range is (-∞,∞)
October 26, 2014

Algebra
for the root, we need x >= 0, or [0,∞) but, the denominator cannot be zero, so the domain is (0,∞)
October 26, 2014

algebra
we want f(2), so that means we need √(x+1) = 2 so, x=3 f(2) = 1/3
October 26, 2014

Algebra
well, where are the denominators zero? x-64 = 0 x^2-64 = (x-8)(x+8) = 0 x^3-64 = (x-4)(x^2+4x+16) = 0
October 26, 2014

Calculus
df/dx = 6(2x+1)^2 so, g' = 1/f' g'(1) = 1/(6*9) = 1/54 check: g(x) = (∛x-1)/2 g'(x) = 1/(6(∛x^2)) g'(1) = 1/(6*9) = 1/54
October 26, 2014

Calculus 1
f'(x) = -3/x e^(1-x^2) (2x^2 lnx - 1) f(1) = 0 f'(1) = -3(1)(-1) = 3 So, now you have a point (1,0) and a slope (3) and the line is y-0 = 3(x-1)
October 26, 2014

calculus
Wow. This one gets tricky, since we're dealing in 3D, rather than the usual 2D. If the bottom of the pole is at B, and the top is at T, and the point directly across the road is at Q, then if the man is x from Q, the diagonal distance across the road (BQ) is y, then y^2 = ...
October 26, 2014

calculus
y = 9√x y(16) = 36 y(25) = 45 So, the secant has slope (45-36)/(25-16) = 1 So, now use the point-slope form to get the equation for a line with slope 1 through (16,36) For the tangent line, the slope y' = 4.5/√x is 9/8 at x=16 Again, use the point-slope form to...
October 26, 2014

Calculus 1
If the hypotenuse has length z, then h^2+36 = z^2 when h=8, z=10 2h dh/dt = 2z dz/dt or, h dh/dt = z dz/dt So, when h=8, 8*2 = 10 dz/dt dz/dt = 1.6 m/s
October 26, 2014

Algebra
GanonTEK is correct. If you don't have ready access to a graphing utility, just use what you know about parabolas. Since this is one which opens downward, it is positive between the roots, where it crosses the x-axis.
October 26, 2014

precalculus
If the cuts are at a distance of x from the center, then since the area of a circular segment is a = 1/2 r^2(θ-sinθ) we want that to be 1/3 of the area, or π/3 r^2 So, 1/2 r^2(θ-sinθ) = π/3 r^2 3(θ-sinθ) = 2π Solve that using your ...
October 26, 2014

Geometry
You have to tell us what angles 1 and 2 are, in terms of the points A,B,C,D.
October 26, 2014

Algebra
since the domain of √u is u>=0, we need 2-x >= 0 That is, x <= 2 Next, we also need 1-√(2-x) >= 0, so √(2-x) <= 1 2-x <= 1 means x >= 1 -(2-x) <= 1 means x <= 3 So, we have a final domain of 1 <= x <= 2 The graph is at http://...
October 26, 2014

Algebra
the denominator cannot be zero. So, x^2+bx+8 must have no real roots. For that to happen, we need the discriminant to be negative: b^2-32 < 0 So |b| <= √32 5 is the greatest integer less than √32
October 26, 2014

science (Need FAST FEEDBACK!!!)
No idea. I'd have to google the terms. Oh, wait, you could have done that just as easily as asking here and waiting for a response.
October 26, 2014

Math algebra
for any radius r, the circumference C is C = 2πr So, just plug in the numbers you have for r
October 26, 2014

math
(4+x)(8+x) = 4*8 + 64 x^2+12x-64 = 0 (x-4)(x+16) = 0 x = 4 So, the rectangle is 8x12 with area 96 (32+64)
October 26, 2014

MATHS
If there were x 50-cent coins, x/6912 = 7/16 x = 3024 So, they collected 6912*.25 + 3024*.50 = $3240.00
October 26, 2014

Calculus
a square encloses the maximum area for a given perimeter.
October 26, 2014

second degree equation word problem
If there are now x rows, then each row has 720/x seats. The new configuration means that (x-4)(720/x + 6) = 720 (x-4)(6x+720) = 720x (x-4)(x+120) = 120x x^2-4x-480 = 0 (x+20)(x-24) = 0 ...
October 25, 2014

Pre-calc
cos(-7pi/6) = cos(7pi/6) = cos(pi+pi/6) = -cos(pi/6)
October 25, 2014

math
See http://www.wolframalpha.com/input/?i=f%3E%3D4 There's a number-line plot there.
October 25, 2014

Precalculus
using the law of cosines, the ship's distance x from the port is x^2 = 170^2 + 90^2 - 2*170*90 cos 14° Now just figure the coordinates of the ship and port to get the desired course. That assumes that there are no cross currents for the rest of the trip.
October 25, 2014

Precalculus
Hmm. Not having the diagram is a bit of a problem. In my diagram, extend the sea-level line TR to intersect PS at Q. Then, I have the angle of depression α = ∠PTR and β = ∠PQR. Apparently that is wrong, so please describe the diagram using only labeled ...
October 25, 2014

Precalculus
I don't see how ∠SPT can be 99°. ∠SPT = ∠SPR + ∠RPT = 51°+69° = 120° Did I miss something in the explanation?
October 25, 2014

Pre-Calc/Trig
you want two factors of 24 which add up to 10. List the factors: 1 2 3 4 6 8 12 24 Take them in pairs, working in from the ends. Note that 4 and 6 add up to 10, so you have (x+4)(x+6) = 0 x = -4 or -6
October 25, 2014

Precalculus
That is the angle between the vectors (7,10,0) and (7,0,3) So since (7,10,0)•(7,0,3) = √149√58 cosθ, cosθ = 49/√8642 = 0.527
October 25, 2014

math
f is increasing where f' is positive f' = 4-3x^2 So, where is 4-3x^2 > 0? similarly for decreasing. max/min where 4-3x^2 = 0
October 25, 2014

math
f' = (x+3) / 4x^(7/4) f' = 0 when x = -3. what about x=0?
October 25, 2014

Math
b = 3j m = 4(b+j) m = 4b+4j m = 4b+4(b/3) m = 16/3 b yes 3 = 1+2 3*8 = (1+2)*8 = 8+16 = 24 (12-4)*(2+1) = 8*3 = 24 12-4*2+1 = 12-8+1 = 5 in the absence of parens, multiplication is done before addition. That's why 3x+2 is (3*x)+2 and not 3*(x+2)
October 25, 2014

math
3*5 = 1/3 * x
October 25, 2014

Algebra
AB has slope 2/-6 = -1/3 So, (y+2)/(6-x) = -1/3 3y+6 = x-6 x=3y+12 So, pick any y and that will give you an x.
October 25, 2014

Calc
since v = 4/3 pi r^3 and a = 4 pi r^2, v = 1/3 ar so, dv/dt = 4pi r^2 dr/dt = a dr/dt so, dr/dt = (dv/dt)/a dv/dt = 1/3 (r da/dt + a dr/dt) = 1/3 (r da/dt + a*(dv/dt)/a) = 1/3 (r da/dt + dv/dt) = 1/2 r da/dt So, 10 = 1/2 (6.5) da/dt da/dt = 3.077 cm^2/s
October 25, 2014

Maty
3d+300m = 111 5d+600m = 198 Now just solve for d and m
October 25, 2014

algebra
check the related questions below
October 25, 2014

Chemistry
11.9g of am carb = 11.9/96.1 = 0.124 moles So, you get 0.248 moles of NH3 0.124 moles CO2 0.124 moles H2O Total moles of gas: 0.496 So, since 1 mole makes 22.4L at STP, adjust for your conditions.
October 25, 2014

college algebra
Using the point-slope form of the line, y-39000 = (64/39)(x-2000) So, when is y > 61000?
October 25, 2014

Physics
a = (36.6 m/s)/(8.22 s) = 4.45 m/s^2 F = ma
October 24, 2014

Calc
who cares about the volume? A = πd^2 dA/dt = 2πd dd/dt Now plug in your numbers to find dd/dt
October 24, 2014

Secondary Math
Hmmm. You have TR(-15x+3) = (-15x+3)(-2x+6) So, TopRight = -2x+6 BC = -3(-5x+1) = 15x-3 So, BottomCenter = 15x-3 That means BottomLeft = 2x-6 TopLeft = (-2x+6)/-3 = 2/3 x - 2 So, the filled-in square is (2/3 x - 2) (-3)(-2x+6) (3)(-5x+1)(-15x+3) (2x-6)(15x-3)(30x^2-96x+18)
October 24, 2014

Algebra
if the domain is all real numbers then the denominator can never be zero. That means it has no real roots. Thus, the discriminant is negative: b^2-32 < 0 So, if 0<=b<=5 x^2+bx+8 is never zero
October 24, 2014

Physic
a = 320km/hr / 6.5s * 1000m/1km * 1hr/3600s = 13.68 m/s^2 Since F = ma, the net force is 13.68m Since the net force is 1.52*10^4-5.2*10^3, divide that by a to get m.
October 24, 2014

MATH HELP asap PLEASE
the vectors to add are v = (550cos7°,550sin7°)+(85cos20°,85sin20°) so, plug in the numbers and get the sum. Then just get |v| and its direction
October 24, 2014

math
.4(6) = 2.4 = 24/10 = 12/5 or, .4 = 2/5, so .4(6) = (2/5)(6) = 12/5
October 24, 2014

Math
correct Though, to save us having to search back for your previous postings, it's better just to add a reply to them yourself. You can see where lots of posts have several replies.
October 24, 2014

Algebra
the denominator cannot be zero. So, its discriminant must be negative. That means 1-4c < 0
October 24, 2014

Math
Unfold the prism into a sheet, and draw a line from one point to the other. Then fold it back up again.
October 24, 2014

math
After Amy, .85 remained. After Beth, .80*.85 = .68 remained After Cathy, .88*.68 = .5984 remained So, 59.84% of the job remained undone. So, how did you arrive at 53%/ It's always good to show your work, so we can check to be sure your logic is correct.
October 24, 2014

Algebra
at x=1, r is undefined (∞) As x gets huge, r-> 0 The denominator is always positive, So, the range is (0,∞) See the graph at http://www.wolframalpha.com/input/?i=1%2F%281-x%29^2
October 24, 2014

Calc
A = πd^2 dA/dt = 2πd dd/dt Now plug in your numbers and solve for dd/dt
October 24, 2014

algebra
we want 23 + 1.75x < 7 + 3x Now just solve for x
October 24, 2014

algebra
that would be x miles, where 45.00+0.25x = 35.00+0.30x Now just solve for x
October 24, 2014

Trig calc
x = r cosθ y = r sinθ Now just plug in your numbers
October 24, 2014

Trig
x = r cosθ y = r sinθ Now just plug in your numbers
October 24, 2014

Math Calc
for any x, sin(x+180) = -sin(x) check the sum formula for sines
October 24, 2014

Math
f(-x) = -x^3+x^2+10x-24 2 sign changes, mean either 2 or 0 negative roots "A few" is not a very precise answer.
October 24, 2014

Math
1 sign change, so there is exactly 1 positive real root. The sign change is from +x^2 to -10x
October 24, 2014

algebra
2f-21 looks good to me. 2f is two times 2f-21 is 21 less than that. good work.
October 24, 2014

math
10+30*2.5
October 24, 2014

Math Trig
h/(120*3) = tan 40 now just evaluate
October 24, 2014

Algebra
we need |500m - 200t| <= 5 where m and t are the rates in $/minute
October 24, 2014

math please help
Not sure how the answer is 16 gallons. Better check my math.
October 24, 2014

math please help
from the Z table, 95% are below 1.645 std above the mean That means .39 + 1.645*.26 = .8177 So, there's a 95% chance that the average consumption is below .8177 gallons For 33 people , that means that there's a 95% chance that .8177*33 = 26.98 gallons will fed them all.
October 24, 2014

maths
a + ar = 28 ar^2 + ar^3 = 252 a(1+r) = 28 ar^2(1+r) = 252 ar^2(1+r)/a(1+r) = r^2 = 252/28 = 9 r = 3 or -3 a(1-3) = 28 ==> a = -14 a(1+3) = 28 ==> a = 7 So, now we need to know that ar^6 = 5103 7*3^6 = 5103 Unfortunately, that works whether r is 3 or -3 Using r = -3 7+(-...
October 24, 2014

Algebra/math 117
well, just count by 6's starting with a1=6: 6 12 18 ...
October 24, 2014

Math
half price is $2/ft^2 so, she paid 2*20 = $40
October 24, 2014

math
42
October 24, 2014

Math
Assuming one side of the run is 19.2, and is formed by the garage wall, then we have 2x+19.2 = 199.4 x = 90.1 ft That assumes also that the door to the run is contained in the garage wall, and thus no gate is needed in the fencing.
October 24, 2014

Need Help asap for math!
the vectors to add are (550cos7°,550sin7°)+(85cos20°,85sin20°)
October 24, 2014

math
12.45*24/1000
October 24, 2014

Math
Draw a diagram of a chord in a circle. In a circle of radius r, a chord of length 2x forms two right triangles where the distance d from the center is found using d^2+x^2 = r^2
October 24, 2014

Trig calc
figure r^2 = x^2+y^2 sin = y/r cos = x/r now just plug in the numbers.
October 23, 2014

science
the upper end. Think of a lever. less force has to be applied at the end, than near the fulcrum.
October 23, 2014

math
If I read it correctly, your dimensions are messed up. A 1x2 matrix * a 2x2 matrix yields a 1x2 matrix. How can y be 2x2? Take a look at this site, and you can enter your matrices using the sample notation. http://www.wolframalpha.com/input/?i=2{6%2C9}*{{27%2C-18}%2C{-12%2C15...
October 23, 2014

Algebra
That's what I get, too.
October 23, 2014

Calculus please help
dP/dR = 36 That is, if R changes by 1, P changes by 36.
October 23, 2014

math
A) x^2+y^3−xy^2=19 2x + 3y^2y' - y^2 - 2xyy' = 0 (3y^2-2xy)y' = y^2-2x y' = (y^2-2x)/(3y^2-2xy) B) Now just plug in the values C) see wolframalpha.com D) ...
October 23, 2014

Science
constant slope means constant speed. positive speed means increasing distance. So, which direction has the distance always increasing?
October 23, 2014

Simple Physics
solids have 3 dimensions planes have two dimensions lines have one dimension so, what do you think?
October 23, 2014

calc
Draw a diagram. When the water has depth y, its surface has width 40+(y/60)(100-40) = y+40 So, the volume of water when depth is y is v = y(40 + y+40)/2 * 7 = 280y + 7/2 y^2 so, dv/dt = 280 + 7y dy/dt Now just plug in your numbers Yeah, I know the units for v are in m-cm^2, ...
October 23, 2014

algebra
ok. what, you want a simpler numeric value for x? All those spaces are confusing, but if you mean log_3(5) * log_4(27) * log_3(√225) that is kinda weird. I suspect a typo. So, using base 3 logs all the way, I get log5*log27*log15 =4log3*2log5 since log_3(3) = 1, that is ...
October 23, 2014

math
If the dimensions are x and y, and assuming you want integer-length sides, the 2(x+y) = 18 x+y = 9 So, just start listing pairs of positive integers that add up to 9: 1 8 2 7 ...
October 23, 2014

Algebra Slope Intercept Form
y(0) = 6 so, y = mx+6 pick any two points to get the slope. For example, (0,6) and (2,0) the slope is -6/2 = -3 y = -3x+6
October 23, 2014

math
If the pieces are in the ratio 3:5 it means that if you divide the rope into 3+5=8 pieces, one part has 3 lengths, and the other has 5. So, since 40/8 = 5, the pieces have lengths 15 and 25 15:25 = 3:5
October 23, 2014

Algebra
Assuming you meant f(x) = 1/(1+(1+1/x)) excluded values occur when 1+1+1/x = 0 2+1/x = 0 x = -1/2 Well, that's probably wrong. How about f(x) = 1/(1+1/(1+1/x)) If 1+1/x = 0, then x = -1 1+1/(1+1/x)) = 0 if x = -1/2 So, now we have three values: 0,-1,-1/2 whose sum is -3/2
October 23, 2014

ap calc
if the bugs collide, then at some point B1 = B2. That means the distance between the bugs is zero, so B1-B2 = 0 (1/2 t^2-t+3)-(-1/4t^2+t+1)=0 3/4 t^2 - 2t + 2 = 0 Since the discriminant is negative, B1-B2 has no real roots. That is, it is never zero. So, the bugs do not ...
October 23, 2014

ap calc
Looks good to me.
October 23, 2014

math Help!!!!!!
We have a winner! But it's usually written a^2 + b^2 = c^2 The caret just indicates a power. In this case, the power is 2.
October 23, 2014

math Help!!!!!!
Surely you remember the 3-4-5 right triangle. Any of the choices look suspiciously similar?
October 23, 2014

Trigonometry
cos2θ = 1 - 2sin^2 θ so, 1 - 2sin^2 θ = 1/2 sinθ 4 sin^2θ + sinθ - 2 = 0 Now just use the quadratic formula to solve for sinθ, then take the arcsin. To check your answer, see http://www.wolframalpha.com/input/?i=cos2%CE%B8+%3D+1%2F2+sin%CE%B8
October 23, 2014

geometry
what is 448.92/12.77 ?
October 23, 2014

math
The smallest factor of x could be 2. So, the largest factor is at most x/2. There's a good chance that there's a prime between x/2 and x. So, start working backwards from x and checking the numbers for primality.
October 23, 2014

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