Friday
July 1, 2016

Posts by Steve

Total # Posts: 41,547

math
you can play around with this stuff at http://davidmlane.com/hyperstat/z_table.html
June 1, 2016

Maths
(x+y)/2 = 7 xy/3 = 16 y=48/x x+48/x = 14 x^2-14x+48 = 0 (x-6)(x-8) = 0 x and y are 6 and 8
June 1, 2016

Polynomials
mine, too.
June 1, 2016

maths
or, you could just solve the two equations using the quadratic formula. That would yield x = [3y±√(5y^2-4)]/2 x = [y±√(152-35y^2)]/6 equate those two and you get y=±2
June 1, 2016

maths
I am assuming you want to solve the system of equations x^2-3xy+y^2+1 = 0 3x^2-xy+3y^2 = 13 from the second, we have xy = 3x^2+3y^2-13 using that in the first, we have x^2-3(3x^2+3y^2-13)+y^2+1 = 0 x^2-9x^2-9y^2+39+y^2+1 = 0 -8x^2 - 8y^2 = -40 x^2 + y^2 = 5 Using that in ...
June 1, 2016

math plz help ;-;
these two make substitution the method of choice. x+y=2 means y = 2-x So, using that in the other equation, 2x-(2-x) = 10 2x-2+x = 10 3x = 12 x = 4 now use either equation to see that y = -2 check: 2*4-(-2) = 8+2 = 10 4+(-2) = 4-2 = 2 similarly, you can substitute for x: x = 2...
June 1, 2016

Precalculs
regardless of the base, log(1) = 0, because x^0 = 1 so, what you have is 6x-12 = 0 x = 2 try writing log_x(n) for log of n (base x). The underscore indicates the base.
June 1, 2016

Math-Calc
you could write f(x) = 7*ln(x^2+5)^-1 then, using the power and chain rules, f'(x) = 7*(-1)*ln(x^2+5)^-2 * (2x) = -14x/ln(x^2+5)^2 f'(1) = -14/(ln6)^2
June 1, 2016

Radicals3
x√(12x^4) = x√(4x^4*3) = x(2x^2)√3 = 2x^3√3 3x√x^2 * 2√x^5 = 6x√(x^2*x^5) = 6x√(x^6 * x) = 6x*x^3 √x = 6x^4 √x -7 = 2-√(12x-3) -9 = -√(12x-3) 81 = 12x-3 84 = 12x x = 7
May 31, 2016

Radicals2
9√72 / 2√24 = 9√(3*24) / 2√24 = 9√3√24 / 2√24 = 9√3/2
May 31, 2016

Radicals
∛-192 = ∛(-1*64*3) = -1*4*∛3 -6∛13) = ∛((-6)^3*13) = ∛(-216)(13) = ∛-2808
May 31, 2016

math plz check ;-; sorry
by definition, (√47)^2 = 47 just as √2 * √2 = 2 (√x)^2 = x That is the definition of the square root of x: the number which, when squared, produces x.
May 31, 2016

math plz check ;-; sorry
so, you're saying that 47 > 50 ?
May 31, 2016

math
one way is just to compute the equations of the lines joining the pairs of points, and show that they intersect in the same point. On the unit circle, let P1 = (1,0) P2 = (cos pi/9,sin pi/9) ...
May 31, 2016

Math
In your equation, p and q are vectors so, find where the y-component is zero.
May 31, 2016

math plz check ;-;
so, you're saying that 47 > 50 ?
May 31, 2016

Algebra
first step: lose the mixed numbers! 5/6-2(-1 3/4)/5 1/5 = 5/6-2(-7/4)/(26/5) = (5/6) + (14/4)*(5/26) = 5/6 + 35/52 = 235/156
May 31, 2016

tripz
This kind of thing is what log tables were used for. Now we have calculators.
May 31, 2016

Statistics
you can find this and other cool answers at http://davidmlane.com/hyperstat/z_table.html
May 31, 2016

Math
He has 9*68=612 points so far He needs 10*70=700 points to achieve his desired average So, haw many more points does he need?
May 31, 2016

Math(Reiny Please Help)
is there something unclear about the solution at http://www.jiskha.com/display.cgi?id=1464662427 ??
May 31, 2016

Math
(4x^2 - 2x-1) - (-3x^3 + 2) 4x^2 - 2x - 1 + 3x^2 - 2 7x^2 - 2x - 3
May 31, 2016

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

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