Saturday
June 25, 2016

Posts by Steve

Total # Posts: 41,425

physics
solve for t in 0.5 - 0.05t = 0
May 31, 2016

Trignometry
maybe you can fix the problem. As it stands, you have mixed up a trig function and the angle: tan(theta+alpha) + 2alpha
May 31, 2016

Math
the area of a circle with radius 15 is pi r^2 = 225pi
May 31, 2016

math
that would be 3(2y) + 1(y+3) = 6y+y+3 = 7y+3
May 31, 2016

math plz help ;-;
the equation of your line is y-8 = -3(x+4) Now massage that to see which choice it matches.
May 31, 2016

math plz help ;-;
plug in the points for your equation: (-4,8): -3(8) = -4-4 -24 = -8 BZZZT! Try again (1,-7): -3(-7) = 1-4 21 = -3 BZZZT! Not that one either.
May 31, 2016

Physics
start: a = v/t = 36km/hr/10s = 3.6 km/hr/s you can convert km/hr to m/s if you desire the usual m/s^2 value. to stop takes twice as long, so a = 1/2 as much.
May 31, 2016

maths
x+y = 14 1/x + 1/y = 7/20 Now just crank it out.
May 31, 2016

maths
3/7 * 3/7
May 31, 2016

Math
42
May 31, 2016

math plz check ;-;
none of those choices matches the equation. It can be written as -3y = 12-2x or y = 2/3 x - 4 And of course, no graphs are shown here...
May 31, 2016

Algebra 1
since distance = speed * time, 7(x+60) = 9(x-60)
May 30, 2016

Math
35000 * (1.05^40-1)/(1.05-1)
May 30, 2016

math
well, he has to make 9 cuts, so 9*10
May 30, 2016

Math2
I assume the bowl is circular, with a parabolic cross-section. If we let the vertex be at (0,0) then we have y = kx^2 where y(15) = 9 so, y = 1/25 x^2
May 30, 2016

Math1
it hits the ground when h=0. So, just solve -12(t+2)^2 + 120(t+2) = 0 or, if you prefer t^2-6t-16 = 0
May 30, 2016

Math (Calculus)
The slope at any point (x,y) is dy/dx = (dy/dt)/(dx/dt) = (2t+1)/(2t) We want to find t such that the tangent line is y=kx (that is, it passes through the origin). At that point y = kx, so k = (t^2+t)/(t^2+3) That means that we need the slope = k, or (2t+1)/(2t) = (t^2+t)/(t^2...
May 30, 2016

Algebra
we want x,y and k such that (x+k)(y+k) = 2xy xy+kx+ky+k^2 = 2xy y = k(x+k)/(x-k) So, there are lots of solutions, with varying dimensions. x y k xy (x+k)(y+k) 2 3 1 6 12 3 10 2 30 60 and so on
May 30, 2016

Math - volume about y axis
The region is bounded above by the x-axis. That is, it is the region below the axis. Since it is symmetric about the y-axis, we really only need to rotate the region from 0 to 1. So, using discs, v = ∫[0,1] πr^2 dy where r = x, so r^2 = x^2 = y+1 v = ∫[0,1] &#...
May 30, 2016

Algebra
arrange the scores in order. The 80th %ile is that score above 80% of the others. Your score is the 78th %ile, so it should be close to the score found above.
May 30, 2016

math plz help ;-;
-2(x-3)+4=8x-20 lose the parentheses: -2x+6+4=8x-20 move all the x stuff to the left, and the numbers to the right: -2x-8x = -20-6-4 simplify each sides: -10x = -30 divide by -10 to get x alone: x = 3 check that it fits the original equation: -2(3-3)+4=8*3-20 0+4 = 24-20 yep
May 30, 2016

math @
finally discovered the difference between () and ||, eh, Stefan?
May 30, 2016

Math
L+K=900 L=K+400
May 30, 2016

Geometry
42
May 30, 2016

algebra
Since the tax is only on the dress, I'd say 10.50 + 12.00*1.09
May 30, 2016

algebra 1
Have you talked to "Ann"? http://www.jiskha.com/display.cgi?id=1464626459
May 30, 2016

Math
This is strange. D(0) = 21 D(8) = 9 D(14) = 0 I am having a hard time relating T values with travel time. Does he server the ball at T=0? Can't be, since then he is 21 ft from the ball. The distance is always decreasing, so clearly the equation describes the return trip ...
May 30, 2016

Math
Draw a diagram. The measures of the angles of triangle PQR are P:43 Q:83 r:54 Now just use the law of sines to get PR: PR/sin83 = 10/sin54
May 30, 2016

Maths
Draw a diagram. The measures of the angles of triangle PQR are P:43 Q:83 r:54 Now just use the law of sines to get PR: PR/sin83 = 10/sin54
May 30, 2016

Physics
I haven't even checked the math, but a water level of 3.26 micrometers? That's barely a film, let alone a depth. give me a break! When you get an answer, at least do a sanity check.
May 30, 2016

Math
well, if their ages now are x and y, then their ages in 7 years will be x+7 and y+7. Now just write your equations and solve them.
May 30, 2016

Math
I assume you meant e^(x-10) = 10 x-10 = ln10 x = 10+ln10
May 30, 2016

algebra
well, just substitute 3 for the b and evaluate the result. 12*(2/3)^3
May 30, 2016

maths
(8+15+x)/3 = 12 now just find x
May 30, 2016

Maths
each interior angle is the supplement of its exterior counterpart. So, the interior angles are 180-60, 180-130, 180-82 The sum of the interior angles is 360, so ...
May 30, 2016

maths
from the garbled language, I assume you want x where (8+15+x)/3 = 12
May 30, 2016

Maths
the other side of the triangle is √(7^2-5^2) = √24 now use that to evaluate the cosine
May 30, 2016

Math
h/20 = tan45°
May 30, 2016

mathss
well, clearly a,b,c are not zero at least one of d,e and f,h is zero.
May 30, 2016

physics
start: a = v/t = 30km/hr/10s = 3km/hr/s If you like, you can convert km/hr to m/s and your answer will be the usual m/s^2. since it takes twice as long to stop, the acceleration is half as much. And negative.
May 30, 2016

Physics
the question has been garbled.
May 30, 2016

SCIENCE PLZZ HELP!!!
#1 and 3 are ok, but the difference between speed and velocity is direction. The magnitude of the velocity is the speed, but the velocity is a vector quantity, which is a directed speed.
May 29, 2016

Math - integrals
x-1 = √5 tan(u) x^2-2x+6 = 5sec^2(u) dx = √5 sec^2(u) du Now plug it into the integral 5∫3 1/(x^2-2x+6)^3/2 dx 5∫3 1/(5sec^2(u))^3/2 √5 sec^2(u) du 5∫3 (√5 sec^2(u))/(5√5 sec^3(u)) du 5∫3 1/(5 sec(u)) du ∫3 cos(u) du ...
May 29, 2016

Math - integrals
x^2-2x+6 = (x-1)^2 + 5 if x-1 = √5 tanu then (x-1)^2+5 = 5tan^2u+5 = 5sec^2u and dx = √5 sec^2u du plug those into the integral and watch things simplify
May 29, 2016

Math3
namely, their average: (a+b)/2
May 29, 2016

Math2
(A) 3 colors, so 4 socks must have two the same (B) Depends on how many pairs of each color. Worst case is if there is only one red pair. Then he might need to take them all.
May 29, 2016

Math (pre-celc 12)
If it is supposed to be 2 * 5^x = 3^(x+1) then just take logs as usual: log(2) + xlog(5) = (x+1)log(3) log2 + xlog5 = xlog3 + log3 x(log5-log3) = log3-log2 x = (log3-log2)/(log5-log3) or, if you prefer, x = log(3/2)/log(5/3)
May 29, 2016

Maths
(5+2x)(12+2x)
May 29, 2016

Integral calculus
A good discussion is found at http://math.stackexchange.com/questions/1379341/how-to-find-the-surface-area-of-revolution-of-an-ellipsoid-from-ellipse-rotating google is your friend.
May 29, 2016

Pre calculus
you need to add/subtract rows and their multiples so the resulting matrix consists of a diagonal of 1's. To start, subtract R1 from R2: x + y + z = -5 0 - 2y + 2z = 4 4x + y + z = -2 Now subtract 4*R1 from R3: x + y + z = -5 0 - 2y + 2z = 4 0 - 3y - 3z = 18 Now work on the...
May 29, 2016

Math
tan(A) = (25-1.5)/23.5
May 28, 2016

math
100,000 * (1+.10/12)^(12*10) = 270,704.15
May 28, 2016

math
The sum-to-product formulas might be helpful here. I think you'll find that the imaginary part is zero.
May 28, 2016

algebra 2
If the downstream rate is x, then since time = distance/speed, 75.5/x + 75.5/(x-5) = 15
May 28, 2016

maths
add up the x- and y-components of the vectors, then convert the result back to distance and bearing.
May 28, 2016

Algebra
this does not factor. The discriminant is negative. b^2-4ac = 36-4*9*8 = -252 The quadratic has two complex roots.
May 28, 2016

Algebra
notice the coefficients are all 2 or 1. So, I'd try 2x^3y^3-x^2y^3 + 2x-y x^2y^3 (2x-1) + 2x-y (x^2y^3+1)(2x-y)
May 28, 2016

Math
That would be (6.3/9) * (10^6/10^2) = 0.7 * 10^4 = 7.0 * 10^3 = 7000
May 28, 2016

Math
5(4-y) = 5*4 - 5*y = 20 - 5y
May 28, 2016

Physics
=? = ↓ ß ≟ xx
May 28, 2016

Algebra
1/a + 1/m + 1/z = 1/2 so, 1/5 + 1/6 + 1/z = 1/2 1/z = 2/15 1/a + 1/z = 1/5 + 2/15 = 1/3 so, Ann and Zack take 3 hours to do the job together.
May 28, 2016

math
original fraction is n/d (n-5)/(d-3) = 1/2 (n/2)/(d+7) = 1/4 Solving these gives n = (d+7)/2, not a single unique solution. Naturally, d cannot be 3, but it is odd, and n must be even, so we can have original fractions of 6/5, 8/9, 10/13, ... or, in general, (2k+4)/(4k+1) for ...
May 28, 2016

Calculus
You should probably solve for y using the quadratic formula. It comes out y = √(2x^3+11) - 1
May 27, 2016

Calculus
http://www.wolframalpha.com/input/?i=%E2%88%AB[1,4]+%CF%80%2825-%285-1%2Fx%29^2%29+dx Did you use ln(x)? If you used base 10, that would be wrong. As you get along in math, you will find the serious folks use log(x) to mean ln(x). It's kind of confusing if you're not ...
May 27, 2016

Calculus
y = 1/x, the x-axis, and the lines x = 1 and x = 4 is rotated about: a) the x-axis: just treat the volume as a stack of thin discs, each of area πr^2, where r=y. So, v = ∫[1,4] π(1/x)^2 dx = 3π/4 = 2.35 rotating about the line y=5, you have to use washers...
May 27, 2016

Pre-Algebra (Check my answers)
Sorry. #1 was correct for 5*3^n
May 27, 2016

Pre-Algebra (Check my answers)
as shown, the table does indeed not represent a linear function. If the 8 was a typo and you meant 9, then y = 8x+9
May 27, 2016

Pre-Algebra (Check my answers)
try using 3^n instead of 3n, which looks like multiplication. |-1| = 1, so f(2) = 2*1*2 = 4 If you actually meant (-1)^x, then f(2) = 2*(-1)^2 = 2*1 = 2
May 27, 2016

Math Help Please? (check my work?)
#1 Why do you start adding 10 each time, when the sequence clearly did not? Try adding 9 instead. #2 ok
May 27, 2016

Algebra - oops
oops. I forgot to carry the denominator along. a/bc - 2b^2/ac - 4c^3/ab
May 27, 2016

Algebra
why all the words? That's what math symbols are for. 2a^2 - 4b^3 - 8c^4 ------------------------ = a-2b^2-4c^3        2abc
May 27, 2016

Calculus
What do you mean by "finding" x,y,z? (x-2)/-1 = (y-5)/5 = (z-7)/7 or x = 2-t y = 5+5t z = 7+7t When x = -3, t=5, so the line passes through (-3,30,42)
May 27, 2016

algebra
I understand csc(A) but have no idea what the Y6 is supposed to mean. If the Y is a typo, then I suppose you could have meant 3csc(A)-6=0 csc(A) = 2 or, if you prefer, sin(A) = 1/2 A = pi/6 or 5pi/6
May 27, 2016

math
C cannot be right, since it only has two terms. Take another stab at it and see whether you can come up with (A)
May 27, 2016

math PsyDAG
well, 1.1*3 = 3.3 so A and B are clearly wrong. when multiplying, add the powers.
May 27, 2016

Geometry
good work
May 27, 2016

MATH - CALC
f = x^3-3x^2 = x^2(x-3) f' = 3x^2-6x = 3x(x-2) f" = 6x-6 = 6(x-1) Now just apply the features you know: f=0: x-intercepts x=0: y-intercept f'=0 ==> critical point f"=0 ==> inflection f'>0 ==> increasing f">0 ==> concave up
May 27, 2016

math plz help
let's do the math in base 10. 325 = 1710 1314 = 2910 x+y+z = 3*17 = 51 x+y = 29 now you can get z, and convert to base 6.
May 27, 2016

math
well, the apothem is 1/2 as long as a side, right? doesn't matter whether it's inscribed in a circle.
May 27, 2016

math
75/.06
May 27, 2016

math
cost = 2400/12*15 revenue = 1350*4 + (2400-1350)/5*8 % gain or loss = ((revenue-cost)/cost - 1)*100
May 27, 2016

maths
whoa - too many = signs!
May 26, 2016

math
by now I'm sure you have figured out what it means to substitute a value, but just in case, that gives you 15+9d = 69 Now you can get d, and thus a+3d.
May 26, 2016

Calculus
dy/dx = √[(x^3)(y)] dy/dx = x^(3/2) y^(1/2) y^(-1/2) dy = x^(3/2) dx y^(1/2) = 1/5 x^(5/2) + c Now if you square both sides, you do not get x^5/25 + c, since (a+b) is not a^2+b^2 But proceeding to find c, √2 = 1/5 + c c = √2 - 1/5 Now square both sides and ...
May 26, 2016

Math
just see which pair of values does not work. replace x and y with the values given: -4(-9)-9 = 36-9 = 27 so it is a solution now try the others.
May 26, 2016

Math
f" < 0 indicates it is concave down. f' > 0 means that the graph is rising. So, an example would be a parabola which opens downward. So, the tangent line at x=0 will be above the curve. draw a graph and it should be clear now.
May 26, 2016

Calculus
right on
May 26, 2016

calc
I find it easier to leave the π in the answer. That way it's exact, instead of some decimal approximation. In any case, I got (a) 20π/9 (b) 125π/27 #2 27π/2
May 26, 2016

calc
#1 (a) discs ∫[0,5] π((5-y)/3)^2 dy (a) shells ∫[0,5/3] 2πx(5-3x) dx (b) shells ∫[0,5] 2π(6-y)(5-y)/3 dy #2 discs ∫[0,9/4] π(((3+√(9-4x))/2)^2-(((3-√(9-4x)))/2)^2) dx shells ∫[0,3] 2πy(3y-y^2) dy
May 26, 2016

Math
draw a side view. r^2 = 6^2 + 4^2 A = 4pi r^2
May 26, 2016

Math
Recall Euler's Formula: V+F-E=2 and check out https://en.wikipedia.org/wiki/Icosidodecahedron
May 26, 2016

Math-Calc
f = 6x(3-2x)^3 f' = 6(3-8x)(3-2x)^2 f(1) = 6 f'(1) = -30 so, the tangent line is y-6 = -30(x-1) see at http://www.wolframalpha.com/input/?i=plot+y%3D6x%283-2x%29^3,+y%3D-30x%2B36
May 26, 2016

Math topic help
well, your answer is the balance after about 15.6 years, so I suspect it's not right. What did you intend?
May 26, 2016

Math (Vectors)
looks good to me.
May 26, 2016

Math (Vectors)
if they are parallel, then the lengths will be proportional. 10/2 = 5, so the ratios of the other dimensions will also be 5:1
May 26, 2016

Algebra II
No, I didn't answer the question, but I gave you enough information so you could complete the solution. Sorry to be jerk-ish.
May 26, 2016

Algebra II
So, with the triangle drawn as you have said, with the right angle on the x-axis, you just have a scaled up 3-4-5 triangle, with sides 15,20,25. sinX = 15/25 = 3/5 cosX = 20/25 = 4/5 tanX = 15/20 = 3/4 Looks like time to review your basic trig functions and the Pythagorean ...
May 26, 2016

College Algebra/Drug Calculations
just multiply numerators and denominators 5/6 * 2/3 = (5*2)/(6*3) = 10/18 = 5/9
May 26, 2016

Calc-Math
just look up the values on the graph and multiply or divide the numbers.
May 26, 2016

maths-word problem
if the digits are t and u, then 10t+u = 6(t+u)-1 t-u = 1 Looks like 65 to me.
May 26, 2016

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