Sunday
December 21, 2014

Posts by steve


Total # Posts: 27,653

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

Algebra
Thank you
October 23, 2014

Algebra
f(n) =3 +4(n-1)
October 23, 2014

Algebra
What function represents the arithmetic sequence 3,7,11,15?
October 23, 2014

Algebra
q = kch^2 Now I guess you can probably solve for c.
October 23, 2014

Calculus
f is increasing where f' > 0 f' = 1/∛(x(64x^3-125))^2 Since (x(64x^3-125))^2 is always positive, f' is always positive, so f is always increasing. f is concave up when f" > 0 f" = (250-512x^3)/(2(64x^4 - 125x) ^(5/3)) So, f"=0 at x = &#...
October 23, 2014

Math
1/A + 1/B = 1/C 1/2 + 1/B = 1/1.25 Now just figure B.
October 23, 2014

Int.science
Assuming the rate was determined by observation, then since it involves measured numbers, it is quantitative Now, if the rate was calculated from physical properties, it'd probably be more theoretical.
October 23, 2014

Math
since all KE was converted to PE, 1/2 mv^2 = mgh v^2 = 2gh Now just plug in the numbers.
October 23, 2014

Math
First figure how many feet are needed, then divide that by 3 to get the yards needed. Then multiply by the price per yard: (10*11)/3 * 13.75 = $504.17
October 23, 2014

Int.science
Looks to me like uncertainty Can't see how size could depict the other characteristics. I can see where a large dot would indicate fuzzy precision, and a small dot would indicate greater accuracy.
October 23, 2014

algebra
just recall that y^a * y^b = y^(a+b) So, you have y^1/3 * y^4/9 - 3y^1/3 * y^2/9 = y^7/9 - 3y^5/9
October 23, 2014

My Bad
Oops. Don't know why I thought she had answered A. Sorry.
October 23, 2014

celebrating Diversity
excuse me? I see no mention of sex anywhere in the statement! It is clearly stereotyping.
October 23, 2014

Algebra
correct. You can easily check your results for yourself at wolframalpha.com
October 23, 2014

physics
what is a "4N point" ? and your cosine hints are mangled.
October 23, 2014

Algebra
What is the 9th term of the arithmetic sequence defined by the rule below? A(n)=-14+(n-1) (2)
October 23, 2014

algebra
note the slope from point to point: (2150-2200)/(20-15) = -50/5 = -10 (2050-2150)/(30-20) = -100/10 = -10 (1750-2050)/(60-30) = -300/30 = -10 So, it looks like F = -10T But, F(15) = 2200, not -150 SO, making that adjustment, we have F = 2350 - 10T
October 23, 2014

Algebra
Sound travels at 343 meters per second. How far does it travel in 8 seconds? My answer is 2,744 meters.
October 23, 2014

Algebra
Thank you -- I'm a gandparent trying to check my grandson's homework
October 23, 2014

Algebra
Is the following relation a function? ((0.3, 0.6). (0.4,0.8), (0.3,0.7), (0.5,0.5))
October 23, 2014

Math (Functions - Word Problem)
what's the trouble? Just sub in the values. Just watch that you change which definition of d(t) you use for the portions of the domain. year t d(t) 2000 0 10.6+0+699 = 699 2001 1 ... ... 2005 5 15.5*5+637 = 7145 2006 6 ... ...
October 23, 2014

trigonometry
If the tower has height h and is at a distance x, then h/x = tan 60° (h-6th)/x = tan 45° Eliminating h, we have x/tan 60° = x tan 45° + 6th x(1-1/√3) = 6th x = 6th/(1-1/√3) whatever 6th is supposed to mean.
October 23, 2014

Maths Question
since y'=0 at x=1,2,3,4,5 the max/min can occur there. But, y' has roots of even multiplicity at x=2 and 4, so those will be inflection points. So, extrema will occur at x=1,3,5 Why? The slope has to change sign at the extrema. If y' has roots of even multiplicity...
October 23, 2014

math
Well, since 7777-4444 = 3333 I've no idea. 7654-4567 = 3087 hmmm. still 90 off So, he must have done 7564-4567 = 2997 or 7654-4657 = 2997 So, he must have transposed two digits as shown above. That, as well as assuming that he could not repeat digits in the numbers.
October 23, 2014

Math
just plug in numbers for the letters a and s, and evaluate the expression.
October 23, 2014

algebra
How about x-3 + x + 2x+1 = 26
October 22, 2014

math
how long is the shelf? I don't feel like searching through all your posts to collect missing data.
October 22, 2014

math
how long is the shelf? You sure you want the thickness of a DVD case in feet?
October 22, 2014

geometry
v = 3.14 * 3^2 * 12
October 22, 2014

pre calc
Use your favorite quadratic regression calculator. I got P = 672.619t^2 - 7863.0952t + 64071.4286 but it's not a very good fit.
October 22, 2014

algebra
Look at the data, using just the changes (1600-760)af/(60-40)°F = 42 af/°F (2020-1600)af/(70-60)°F = 42 af/°F (2650-2020)af/(85-15)°F = 42 af/°F I guess that tells the story, eh?
October 22, 2014

math
3/4 + 1/9 find each sum
October 22, 2014

college algebra
C(t) = 14500 + 6.75t
October 22, 2014

Algebra Slope Intercept Form
or, just y = 1/5 x
October 22, 2014

Algebra Slope Intercept Form
correct
October 22, 2014

Calc
f(0) = 1+0 = 1 f(2pi) = 1+0 = 1 f'(x) = -sinx + 2sinx cosx = sinx(2cosx-1) So, f'=0 at x=0,pi,2pi and pi/3,5pi/3 f(pi/3) = 1/2 + 3/4 = 5/4 f(pi) = -1+0 = -1 f(5pi/3) = 1/2 + 3/4 = 5/4 Looks like the min is -1 and the max is 5/4 See http://www.wolframalpha.com/input/?i=...
October 22, 2014

arithmetic
If you want to find 8-0, recall that 8-8 = 0 so, 8-0 = 8 9-3? 9-6=3, so 9-3=6 Just google subtraction related facts, and study up some.
October 22, 2014

Algebra
the minimum point on a parabola is its vertex. So, find the vertex. For y = ax^2+bx+c, the vertex is at x = -b/2a. In this case, that is x = -12/2 = -6 AT x=-6, y = -31 This can be seen by rearranging the equation into the vertex form. x^2+12x+5 = (x^2+12x+36) + 5 - 36 = (x+6...
October 22, 2014

math expressions
b = 2g+5 b+g = 89 so, 2g+5+g = 89 Your question is a bit garbled, but I expect you can devise an answer using the above equations.
October 22, 2014

Science Density
well, the volume of water displaces is 150*90*8 cm^3 If the person is floating, her mass is the same as the water displaced. If the person is submerged completely, her volume is the same as that of the water. So, if you know the person's density, that can be used. If ...
October 22, 2014

Not So Fast
Not so fast. We have the hypotenuse = 17 x^2 + 15^2 = 17^2 x = 8 So, B is correct
October 22, 2014

Math
f = x^(1/6)−x^(−5/6) f' = (1/6)x^(-5/6) + (5/6)x^(-11/6) = (1/6)x^(-11/6)(x+5) so, where is f' = 0?
October 22, 2014

Math
-2x^2-8x+17 = -2(x^2+4x) + 17 = -2(x^2+4x+4) + 17 + 2*4 = -2(x+2)^2 + 25 Now just read off the vertex.
October 22, 2014

Trig
If you mean cot(θ-π/2) then that's easy just as sinθ = cos(π/2-θ), tanθ = cot(π/2-θ) and, since cot(-θ) = -cotθ, cot(θ-π/2) = -cot(π/2-θ) = -tanθ Oh, well, if you must, show that cot(θ-π/2...
October 22, 2014

math
whatever do you mean by "next level"?
October 22, 2014

Algebra 1
I think that the level of problems presented indicates the intent is -2/5 x - 9 < 9/10 -4x - 90 < 9 -4x < 99 x > -99/4
October 22, 2014

Algebra
since time = distance/speed, you have d/(150-30) + d/(150+30) = 3 Now just solve for d
October 22, 2014

maths
the game is 120 minutes long. He misses the goal if he arrives during the last 100 minutes, so p = 100/120
October 22, 2014

Algebra
3*120 <= 135+145+x <= 3*130 360 <= x+280 <= 390 80 <= x <= 110
October 22, 2014

algebra
If the short side is x, then x + x+6 + 2x-2 = 24 Now, just find x and figure the sides.
October 22, 2014

math
30 incorrect means 30(1 1/2)=45 correct. So, how many altogether?
October 22, 2014

maths
14000(1 + .12*2)
October 22, 2014

Trigonometry
356
October 22, 2014

physics
no idea - what is it filled with?
October 22, 2014

statistics
12500 rec * 30min/rec * 1hr/60min * 1emp/2080hr = (12500*30)/(60*2080) = 3.0 emp
October 22, 2014

math
pure gold is 24K, so 22K gold is 22/24 = .917 18K gold is 18/24 = .750 14K gold is 14/24 = .583 The problem clearly has a typo when it mentions 18K gold. A 22K statue the same weight as a 14K statue contains more gold. The difference is (22-14)/24 * 73.5 or, given all the ...
October 22, 2014

math
15*852 = 12,780 assuming all those who bought tickets watched the show ...
October 22, 2014

Math
well, check your math. Starting with $60, that means 20 on books, leaving 40 16 on games, leaving 24 6 on DVD, leaving 18 3 on candy, leaving 15 We have a winner! Your final step in concluding that if 1/4 of the money is $15 then the whole was $60 is correct. But your original...
October 22, 2014

physics
s = vt + 1/2 at^2 Now just plug in v=247, a=28, t=8.7
October 22, 2014

math
if the model has diameter 31.9 cm, its area is π*31.9^2 = 3196.92 cm^2 So, divide that by 2 and then by 10 to get the number of jars
October 22, 2014

Math 222
in the first, each term contains a power of a and a power of b. You need to find the highest power of a and b that divides each term. That would look like a^2 a^2 b + a^2 b^2 b Now factor out the a^2 b, leaving the indicated solution. Recall that a^m a^n = a^(m+n) Review the ...
October 22, 2014

physics
constant speed means zero acceleration!
October 21, 2014

Math 222
I assume you want to factor the expressions? a^4b + a^2b^3 = a^2b(a^2+b^2) z^2 + 18z + 45 = (z+3)(z+15)
October 21, 2014

calculus
arcsin(ix) = i arcsinh(x)
October 21, 2014

math
600rev / (44 8/9 rev/min) = 13 37/101 min
October 21, 2014

Physics
(83.59)(1.44/9.81)
October 21, 2014

math
come on 1/2 = .5000 2/3 = .6666 So, anything in between, such as .58345... .66217...
October 21, 2014

math
24/18 = 4/3 6.12/4.5 = 1.36 That's pretty close to the same ratio, so just scale up by 18/4.5 = 4 Just multiply each dimension by 4. That will produce a size of 18 by 24.48
October 21, 2014

Math
the sides are 22,x,2x-2, so we have 2x-2-x < 22 < 2x-2+x x < 24 < 3x So, it looks like 8 < x < 24
October 21, 2014

Trigonometry
what you have is cosθ + 1 = 2cos^2θ - 1 2cos^2θ - cosθ - 2 = 0 so, solve that quadratic for cosθ and pick the choice.
October 21, 2014

Algebra
d = 2q 5n+10d+25q = 440 There will probably be no single solution, since you only have two equations.
October 21, 2014

Math HELP!
A. No - 3.2 is real, not integer B. true C. No - 2/3 is not a perfect square D. No - NO integer is irrational You were just guessing, I presume.
October 21, 2014

math
there is only one answer. I guess they want you to attack it in three different ways. Seems kind of pointless to me.
October 21, 2014

maths
just set up the equations: a+2d + a+6d = 38 a+8d = 37 Now just solve for a and d.
October 21, 2014

Algebra
the second car is going 15 mph faster than the first when the 2nd cars starts out, the 1st car has gone 50 miles already. So, how long does it take to make up 50 miles, going a relative speed of 15 mi/hr?
October 21, 2014

Math
just set up two expressions for the costs, and set them equal. For m minutes, you want .08m = 6.00 + .02m Now just find m which makes the two values equal.
October 21, 2014

Algebra: Answer Check
looks good to me.
October 21, 2014

Calculus
It appears you are trying to approximate ∛7.9 So, if y = ∛x, then dy = 1/(3∛(x^2)) dx at x=8, y=2, so if dx = -0.1, dy = 1/(3∛64) (-0.1) = -1/240 = -.0042 So, ∛7.9 ≈ 1.9958 check: ∛7.9 is 1.9916 The estimate is expected to be a bit ...
October 21, 2014

Homework (Science)
it hits the ground when the height is zero. So, just solve 32.5t - 4.9t^2 = 0
October 21, 2014

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