Saturday
July 4, 2015

Posts by STEVE


Total # Posts: 32,100

mth121
2x+3y = 3 x-2y = 5 has solution (3,-1) This point is also on on the third line, so it is the solution to all three equations.
May 3, 2015

Math 222
a good place to start would be here. Does your text not have any examples of graphing functions? http://www.wolframalpha.com/input/?i=plot+y%3D-x%5E2%2C+y%3D%E2%88%9A%28x-1%29
May 3, 2015

math
y = -(10-x)^2+75 This is just a parabola with vertex at (10,75) So, the max height is 75 meters
May 3, 2015

Maths
The 4 points define a tetrahedron. What do you mean by "boxes" as related to the tetrahedron?
May 3, 2015

trigonometry
done. see earlier post.
May 3, 2015

trigonometry
just pull out your calculator. cos(1.50) = 0.07 Since cos x > 0 in QI and QIV, the other solution is 2π-1.50
May 3, 2015

trig
Trying to get past the copy/paste of strange fonts, I interpret the question as finding the trig functions of the angle whose terminal side is (√15,8) You have x=√15 and y=8, so r = √(15+64) = √79 Now just use the definitions sinθ = y/r cosθ...
May 3, 2015

Math
You don't need it. arctan(-x) = -arctan(x) So, now you want arctan(-tan(7/15π)) = -arctan(tan(7/15π)) = -7/15π
May 3, 2015

Math
tan(-22/15π) -tan(22/15π) -tan(π+7/15π) -tan(7/15π) not a recognizable value. As long as you have to use your calculator anyway, why nut just plug in the original value? You get -9.514 Or is there more to the question than what you posted?
May 3, 2015

math
Try this, which is a better rendering of the given statements: x+23 = 2y y+23 = 3z z+23 = 4x
May 3, 2015

Physics Help Please
just review your formulas. In particular, hi/ho = f/f-do 32mm/17m = 40mm/(40-do)mm 32/17000 = 40/(40-do) do = 21210mm = 21.21m
May 3, 2015

Math
let u = arcsin(x) then du = 1/sqrt(1-x^2) dx now your integrand is just 1/u du Think you can handle that one?
May 3, 2015

physics
since there is no friction, there is no horizontal force. Thus, no acceleration. So, think of Newton's 1st law of motion.
May 3, 2015

Chemistry
Given the very nature of the question, you must have studied some examples. Care to share your ideas on the topic?
May 3, 2015

Trigonometry - PS
However, since inverse trig functions have principal values (because they are multi-valued), you have to be careful. arctan(tan(3π/4)) = arctan(1) = π/4, not 3π/4. So, you need to reduce your fraction to see how many multiples of π you can discard, and then...
May 3, 2015

PHYSICS
That would be zero, of course. Care to rephrase the question?
May 2, 2015

algebra 1
with the exception of calling the vertex the axis of symmetry, yes. The axis always passes through the vertex, but it is not the vertex; the vertex is just a point. The axis has no minimum point; it is a line.
May 2, 2015

algebra 1
axis is the line x=0
May 2, 2015

algebra--1 question
recall that (a+b)^2 = a^2 + 2ab + b^2. So, (2√5+3√7)^2 = (2√5)^2 + 2(2√5)(3√7) + (3√7)^2 = 4*5 + 12√35 + 9*7 = 83 + 12√35
May 2, 2015

calculus
see related questions below
May 2, 2015

Optimization Calculus
so, now go for it. You know that 2x+y = 96, so y = 96-2x the area is xy = 2x(96-2x) = 192x - 4x^2 That's just a parabola; its vertex gives the maximal area.
May 2, 2015

math 1
42
May 2, 2015

Calculus
something wrong with Reiny's solution? See http://www.jiskha.com/display.cgi?id=1430504193
May 2, 2015

Maths(URGENT ANSWER please )
you have sum[1,∞] 2n/n! = 2 sum[1,∞] 1/(n-1)! = 2 sum[0,∞] 1/n! recall that e = 1 + 1/1! + 1/2! + 1/3! so, your sum is 2e
May 2, 2015

Calc 1
y' = 2(x-5) Let x0=1 x1 = 1 - y/y' = 1 - 16/-8 = 3 x2 = 3 - 4/-4 = 4 x3 = 4 - 1/-2 = 6 x4 = 6 - 1/2 = 5.5 and so on for six decimal places.
May 2, 2015

Maths(URGENT ANSWER please :
sum[1,∞] 2n/(n+1)! = 2 sum[1,∞] n/(n+1)! = 2 sum[1,∞] (n+1-1)/(n+1)! can you take it from there?
May 2, 2015

Algebra
recall that a^3-b^3 = (a-b)(a^2+ab+b^2) You have 3^3 - (m+2n)^3 = (3-(m+2n))(3^2 + 3(m+2n) + (m+2n)^2) = (3-m-2n)(9+3m+6n+m^2+4mn+4n^2) I think I like the original way more . . .
May 2, 2015

Calc 1 - ouch! (duh)
I sure flubbed that one. Your later solution was spot on, Reiny.
May 2, 2015

Calc 1
Naturally, the tangent with the largest slope will be the one closest to the origin. So, we want -6cosx = -6sinx/x x = tanx solve that using Newton's method, and you have x = 4.93 so, your line is y = -6cos(4.93)(x-4.93)+6sin(4.93) or y-5.98 = 0.52(x-4.93) See the graphs ...
May 2, 2015

Physics Help Please --- Urgent
since the rays from the building may be considered parallel, we have f = 24. So, to find the distance of the insect's image (from the lens), 1/16 + 1/x = 1/24 Use that to arrive at your final answer.
May 2, 2015

Math
since t=0 when y is a max, we will have y = a cos(kt) the radius is 5, so y = 5cos(kt) the period is 1/25 min, so k/2pi = 1/25 k = 2pi/25, and thus y = 5cos(2pi/25 t)
May 1, 2015

Math- Trigonometric Functions
since the curve starts at the top when t=0, y = a cos(kt) the diameter is 10, so the radius is 5: y = 5 cos(kt) The period is 1/25 min, so 2pi/k = 1/25, making k = 2pi/25 y = 5 cos(2pi/25 t) Not sure what you mean by the blade's distance from the center. I think you meant ...
May 1, 2015

Algebra
b + 2(2b-0.3) = 4.9 That gives the base; now figure the legs.
May 1, 2015

college precalculus
a = 1/3^6 r = 1/3^2 S = a/(1-r) = (1/3^6)/(1-1/9) = (1/3^6)(9/8) = 1/648 a = -100/9 r = -3/10 S = (-100/9)/(1+3/10) = -1000/117
May 1, 2015

Trigonometry
Assuming that the first-named point on the opposite side (P) is the point directly opposite from the point on his own side (Q), then we have, if the observer is point O, m<POQ = 28 m<OQP = 128, so m<OPQ = 24 Now, using the law of sines, if the width is w, we have w/...
May 1, 2015

math ( help please instantly )
just a little synthetic division trying to find a root. Cubics are not always easy to factor by inspection.
May 1, 2015

math ( help please instantly )
m^2-7m+12 = (m-3)(m-4) m^3-2m^2-2m-3 = (m-3)(m^2+m+1) so, LCM = (m-3)(m-4)(m^2+m+1) Now try the others. What do you get?
May 1, 2015

Maths
p = √(32/6)
May 1, 2015

Math
It's always easiest to convert mixed numbers to improper fractions. for adding, find the lowest common denominator for multiplying, just multiply/divide 9 9/10 × 8 8/9 = 99/10 * 80/9 = 88 15 11/15 + 14 5/9 + 7 3/5 = 708/45 + 655/45 + 342/45 = 1705/45 = 341/9 = 37 8/9...
May 1, 2015

Math
3^3 = 27, not 18 4 * 27 -54÷6+25 Just as multiplication/division are done left to right, so are addition and subtraction 108-9 +25 99+25 124 Besides the typo of 26, you did 72-(9+26), not 72-9+26 314-3 [2^5 -(9- 4 ) ^2 +3]^2 314-3 [2^5 - 5^2 +3]^2 314 - 3[32-25+3]^2 314...
April 30, 2015

Math
so, show us your work, and we'll check it.
April 30, 2015

Calculus
the area of a triangle of side s is √3/4 s^2 So, if the triangles have side x and the tent has length y, we have (√3/4)x^2 * y = 2.2 the area of cloth used is a = 2(√3/4)x^2 + 3xy and the cost c is c = 1.4(2(√3/4)x^2 + xy)+xy Now just find dc/dx, after ...
April 30, 2015

algebra please help
I only see one polynomial.
April 30, 2015

Trigonometry
hey, come on. The y-intercept is where x=0! So, just plug it in y(0) = -2 sin(0-pi/2) = -2(-1) = 2 getting x-intercepts can be hard. Getting the y-intercept is trivial! Don't forget your Algebra I now that you're in trig.
April 30, 2015

Trigonometry
the origin is an x-intercept if f(0) = 0. Is that true here?
April 30, 2015

Advanced Functions
sin4x/(1-cos4x) (2 sin2x cos2x)/(2sin^2 2x) cos2x/sin2x (2cos^2 x - 1)/(2sinx cosx) cosx/sinx - 1/(2sinx cosx) cotx - 1/2 cscx secx
April 30, 2015

Math
the diameter is 14, so the radius is 7 the area is π*7^2 = 49π
April 30, 2015

Math
One way: divide the big volume by the small volume: (3 3/4)(5)(4 1/2) / (1/4)^3 = (675/8) / (1/64) = 5400 Another way: decide how many cubes it takes to fit each of the larger dimensions (3 3/4) / (1/4) = 15 5 / (1/4) = 20 (4 1/2) / (1/4) = 18 So, the prism is 15x20x18 cubes...
April 30, 2015

Math
y=x+(x/4) ? Why not just 5/4 x? Once you get your curves figured out, r = the distance to the inside curve R = the distance to the outside curve You need to solve for x, so you know r. Clearly, R=3, since that's the far boundary. The limits of integration (along dy) are ...
April 30, 2015

Math
assuming the cylinder also has diameter 7, then if the cone has height h and the cylinder has height k, you need π/3 * r^2 h = π * r^2 k h/3 = k The cone needs to be 3 times as tall as the cylinder
April 30, 2015

math
Draw a diagram. You have a 30-60-90 triangle, with the tree at the right angle. You want the altitude from the tree to the road. The distance of the tree from B is 200 The distance of the tree from A is 200√3 So, h = 100√3
April 30, 2015

Calculus
with 3 unknowns and only two equations, there will be no unique solution. It should be 13y+5z = 39 so, pick any y and z that fit, and then figure x. Or, you can evaluate y and z in terms of x: y = 5x-7 z = 13(2-x) Now you can pick any value for x, and then figure y and z. In ...
April 30, 2015

Math
1982: (3.35*40+80)(50) = 10700 2015: 10700*1.045^(2015-1982) = 45732.12
April 30, 2015

Math
317.24(1.085)(1.15)+25.00
April 30, 2015

Calculus
just add the vectors. That is the resultant, call it r. The equilibrant is -r: that vector which cancels the resultant, keeping things in equilibrium.
April 30, 2015

Calculus
vectors are just a compact way of describing three independent sets of numbers. You just have 3a-6 = -3 9-2b = 1 6-2b = -2 clearly, a=1, and any value of b will work. since (1,3,2) and (3,b,b) are not collinear, they span R2.
April 30, 2015

Math
pq-pr-qp+qr-rp+rq or, arranging factors alphabetically, pq-pr-pq+qr-pr+qr -2pr+2qr 23ab-12ab - 12bc^2-13bc^2 11ab - 25bc^2
April 30, 2015

Math
just plug and chug: 2(-7/2)^2 - 9(-7/2) + 7 ...
April 30, 2015

Math
nothing to solve. just evaluate the expression 3(-1.3)(2/5) - |-1.3-2| -1.56 - |-3.3| -1.56 - 3.3 -4.86
April 30, 2015

Math
(3245.50-143.15)(1-0.10) = 2972.115
April 30, 2015

Calculus
dy/dx = (1+x)/xy y dy = (1+x)/x dx 1/2 y^2 = lnx + x + c since y(1) = -4, ln 1 + 1 + c = 8 c = 7 1/2 y^2 = lnx + x + 7 . . .
April 30, 2015

math
pi * 9^2 * 4
April 30, 2015

math
if the digits are a,b,c we see that a=4 Then we are doomed. If b and c are both odd, they cannot sum to 5, which is also odd. And how about a little punctuation? That run-on sentence is very annoying.
April 30, 2015

Algebra 2
Is there a question in there somewhere?
April 30, 2015

math
just subtract what was used from the original amount: 9100 - 321*28.286 However, that assumes that all the leftover parts could be combined to form new circles; not very likely. A better way to look at it is to decide how many rows and columns of discs could be cut. 130/6 = 21...
April 30, 2015

SOLVE -MATH
9C6 * 6C3
April 30, 2015

physics
we have, since the focal length is constant, 1/f = 1/20 + 1/x = 1/16 + 1/(x+2.7) Just solve for x, and then find f.
April 30, 2015

Calculus
good work. Confirm with the graphs at http://www.wolframalpha.com/input/?i=plot+x%5E2%2B3x%2B2%2C+y%3D3x%2B2+for+-1+%3C%3D+x+%3C%3D+1
April 30, 2015

maths
you have a common ratio, so p/-6 = -32/p p^2 = 192 ...
April 30, 2015

math
No, P(black) = 9/10 1 - 9/10 = 1/10 B is the odds of drawing a white, not the probability.
April 30, 2015

Physics
1A is 1C/s You have 73mC/9s = 8.11mA the net charge is not relevant here, since all we need is the number of Coulombs.
April 30, 2015

MAT 142
keeping all the measurements in yards, (15/3)(8/3)(8/36)($30)
April 30, 2015

Math
clearly you can drop the trailing zeros, getting 504/5940 both are even, so you can factor out 2 top and bottom: 252/2970 and again: 126/1485 now 3's: 42/495 and again: 14/165 That's as far as you can go. Or, you can factor both numbers. 5040 = 2^4 3^2 5 7 59400 = 2^3 ...
April 30, 2015

Math
(8*7)/2 - π/4*3^2
April 30, 2015

math
hmmm. None of the polynomials factors over the reals, so I don't see any help there. Looks like GCF=1 and LCM = (1+4x+4x^2-16x^4)(1+2x-8x^3-16x^4)(16x^4+4x^2+1) if x=-1 we have -17,-7,21 x=0 we have 1,1,1 x=1 we have -7,-21,21 x=2 we have -231,-315,273
April 30, 2015

math - eh?
what's with the .. ?
April 30, 2015

Math
first expand: 4x^3y+30x^2y-35xy^2-72x^2y+80xy^2-11xy^2 then combine: 4x^3y-42x^2y-34xy^2
April 30, 2015

Math
(4)(14)+(-1)(3)+(-6)(8) = 56-3-48 = 5 Pretty grim score, eh?
April 29, 2015

English
What do you do when the author can't be found? How do you cite the book? Would use just the title of the book or explain that the info is missing?
April 29, 2015

English
what should you do if you need to cite a book for which you don't know the author?
April 29, 2015

Algebra 2
multiply through by 8x and you have 2(x+2)-3(4) = x 2x+4-12 = x x = 8 check: 10/32 - 3/16 = (10-6)/32 = 4/32 = 1/8
April 29, 2015

Math
to be a perfect square, all its prime factors must be squared. Since 7 occurs an odd number of times, 7^2 cannot divide the number. So, no, it is not a perfect square. It is almost a perfect square, though, since 2^6 * 3^10 * 5^12 * 1^18 = (2^3 * 3^5 * 5^6)^2
April 29, 2015

Math
6789 = 3*31*73 since 3,31,73 all divide the first term, and 6,62,146 all divide the second term, 6789 divides both terms, and thus the sum as well.
April 29, 2015

Math
all the powers must be a multiple of 3. So, it is a perfect cube. It is (2^3 * 3^4 * 5^2 * 7)^3
April 29, 2015

MATH
d = 7n 10d = 650+5n 10(7n) = 650+5n 65n = 650 n=10 so, d=70
April 29, 2015

Molar mass
so, what steps did you follow? If you want help with your error, show your work...
April 29, 2015

Mathematics
just plug and chug: 148225 - x^2 = 578132.1225 - 406278.76 + 1274.8x - x^2 x = -18.535
April 29, 2015

pressure
PV=nRT Just plug in your numbers and solve for P.
April 29, 2015

math
440x220 with the 440' side parallel to the river. the related questions below provide steps for the solution.
April 29, 2015

Math
if it is a perfect square, all of its prime powers will be even. Since if you have (2^a 3^b 5^c ...)^2 all the exponents are doubled.
April 29, 2015

math: fundamental counting principal
12*10*7*5
April 29, 2015

math; solve problem
the simplest solution is 32.2*21/13.65
April 29, 2015

Math
The problem is poorly worded. Why don't you draw a diagram, and tell us what the relevant points of reference are?
April 29, 2015

MATH; STANDARD DEVIATION
you can plug in your numbers and play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
April 29, 2015

Algebra
y=0 at x = -1 for x > -1, y is increasing
April 29, 2015

Pressure
PV=kT, so P/T is constant Figure the increase in T (as a factor), and apply that same factor to P to keep the ratio constant.
April 29, 2015

Math Help
what, you can't plug in values for n? a1 = 1(1^2-6) = 1(-5) = -5 a2 = 2(2^2-6) ... a1=14 a2 = (-2)(14) = -28 a3 = (-2)(-28) ...
April 29, 2015

Math
GCF=1 LCM=pq
April 29, 2015

math
3x2 + 3x5 = 6+15 = 21 8x3 = 18 So, he needs more canvas than he has. Or, you could line up the two desired pieces, and he needs one large piece 3x(2+5) = 3x7, but his piece is only 3x6.
April 29, 2015

algebra NEED HELP
√(x-5) is always positive. So, there is no solution √(2-7x) = 2x 2-7x = 4x^2 4x^2+7x-2 = 0 (x+2)(4x-1) = 0 so, x = -2 or x = 1/4 But since √(2-7x) is positive, x = -2 is an extraneous solution So, x = 1/4 is the only solution
April 29, 2015

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