Saturday
August 27, 2016

Posts by steve

Total # Posts: 42,826

PHYSICS
F=ma the tension in the string is the downward weight of the 2kg mass. The force on the 3kg mass is that weight.
June 21, 2016

math
Draw a diagram. If the chord has length 2x, then x/200 = sin 34°
June 21, 2016

maths
That would be 8(1+2+3+...+14+15) You can find the sum of the first n numbers, right?
June 21, 2016

maths
using the law of cosines, AC^2 = 96^2 + 80^2 - 2*96*80 cos56°
June 21, 2016

math
3/8
June 21, 2016

math
1/5 * 3/4
June 21, 2016

Maths
20m^2 * 1.5m * 1000L/m^3 ---------------------------- = 600 min        50 L/min
June 21, 2016

CALCULUS
The graph should make things clear: http://www.wolframalpha.com/input/?i=%7Cx%5E2%2F2-2%7C
June 21, 2016

Math
14
June 21, 2016

maths
ok now you do the same.
June 20, 2016

Math
Let z = x+yi Then we have x^2+y^2-2x+2yi+xi-y=2i That means we have x^2+y^2-2x-y = 0 2y+x-2 = 0 Thus, x = 2-2y and so 4-8y+4y^2+y^2-4+4y-y = 0 5y^2-5y = 0 5y(y-1) = 0 so, y=0 x=2 or y=1 x=0 Or, z=2 or z=i I'll let you verify that both of those z values satisfy the original...
June 20, 2016

CALCULUS
surely the initial mass is positive. Kind of makes things more real. Looking at the original equation, if y(0) < 0, we have exponential growth, not decay.
June 20, 2016

CALCULUS
this is just like the other one. You already know about radioactive decay, and how it is an exponential function, right?
June 20, 2016

CALC PLEASE HELP
dy/dt = ky dy/y = k dt ln y = kt + ln c y = c*e^(kt) Now plug in your values to determine c and k.
June 20, 2016

maths
triangles BDA and BDC are congruent.
June 20, 2016

Calculus
you can find the area B of the base (a triangle), and its height (the z-intercept) v = 1/3 Bh
June 20, 2016

Math (pre-celc 12)
the order does not matter. There are 21P3 ways to select an ordered group of 3 items from 21. Whoever is chosen first, there are 21 available people. 20 for the 2nd, and 19 for the 3rd.
June 20, 2016

Math
So far you have only mentioned 4 places. Any data on the other three? A lot of possibilities will fit what you have required so far.
June 20, 2016

physics
10+12 √(10^2+12^2)
June 20, 2016

algebra
2x+2x+2+2
June 20, 2016

Science chemistry
I only found TETRACHLOROMETHANE
June 20, 2016

Maths
(n+1)/d = 1/3 n/(d+1) = 1/4 If that's too hard to work through, then just consider that 5/15 = 1/3 4/16 = 1/4
June 20, 2016

Mathematics
14000(1+.12)^2 vs 14000(1+.12/2)^(2*2)
June 19, 2016

math
2(r^4-1)/(r-1) = 30 r=2 The last 4 terms don't matter, unless you are interested in how many there are.
June 19, 2016

Math
t+b+f = 7.56 f = 2t 1.1t + 1.25b + f = 8.68 Now just crank out the desired answers
June 19, 2016

Maths
w/250 = cot50°
June 19, 2016

Physics
How can you explain work, in regards to electricity? I understand it as the product of energy used, usually displacement. I cant understand or explain it as far as electricity is concerned. I'm not sure if I understand it at all.
June 19, 2016

Math
oops. 2sin^2(1/2 y) = 1 - cosy
June 19, 2016

Math
f(x+y)-f(x) = sinx cosy + cosx siny - sinx sin^2(1/2 y) = 1 - cosy That should get you on your way... The rest is just algebra.
June 19, 2016

trigonometry
draw a diagram review the tan function see that tanθ = 36/20
June 19, 2016

Maths
It never hurts to review. I help students with advanced algebra and calculus, and am constantly amazed and frustrated at how much of their elementary arithmetic they have forgotten. Look over your topics, try out some problems, and make sure that when you see them you don'...
June 19, 2016

math
if sinθ = 1/3, 2cot^2θ + 2 = 2csc^2θ = 2(3)^2 = 18 = (9)+(224) = 233
June 19, 2016

math
just subtract (5x^3-13)-(2x^3-4x+9) = 3x^2+4x-22
June 19, 2016

mathematics
.0x0 .3x1 .6x2 .9x3 .000 .341 .682 Can't pin it down any better than that
June 19, 2016

Math 5
If there were 15 correct answers, then there were 5 wrong, so 15*5 + 5*2 = ?
June 18, 2016

math
Tn = 2n
June 18, 2016

Math
1.4/7
June 18, 2016

Math
The speeds are x and x+8 since distance = speed * time 60(x + x+8) = 4320
June 18, 2016

math
a = 5-2√6 a^2 = 49-20√6 1/a^2 = 49+20√6 Now just add up a^2 + 1/a^2
June 18, 2016

Mathematics
surely you can do some of those. Which ones present a problem? area of sector: 1/2 r^2 θ arc length: rθ
June 18, 2016

Mathematics construction
ok now what? Surely you can bisect a 90-degree angle...
June 18, 2016

math @Reiny
oh, yeah. Good call.
June 18, 2016

math
well, geez, just plug in the values. You have (x-1)(x+3) = x^2 + 2x - 3 = x^2 + (a+1)x + b Now it should be clear what a and b are if the two polynomials are identical.
June 18, 2016

math
If I read you right, we have v^2 + 4√3 v - 15 = 0 (v-√3)(v+5√3) = 0 Not sure what you mean by "its coefficient".
June 18, 2016

Science
it is at its highest when the velocity drops to zero and it starts to fall. v = Vo - at = 98 - 9.8t ...
June 18, 2016

math
see earlier post
June 18, 2016

physics
F = ma now just plug in your values.
June 18, 2016

area of a circle
clearly the radius is 3, since that's how far away the point is from the x-axis, right? Now crank it out.
June 18, 2016

Algebra
well, they have said that a=3 r=5 The 23rd term is thus 3*5^22 That is, you start with 3 and multiply by 5 22 more times to get to the 23rd term. Next, we have a + 7*4 = 13 so, a = -15 T23 = -15 + 22*4 Any two consecutive terms of a geometric sequence have a common ratio. In ...
June 17, 2016

math
The multipliers are 1,3,9,27, ... As powers of 3, those are 0,1,2,3,... You can't say 7*3^x because the first term (x=1) has not been multiplied yet.
June 17, 2016

math
I can see only (5,-5) and (-5,5) any other pairs of additive inverses do not differ by 10
June 17, 2016

Math
terms of what?
June 16, 2016

math
since mass is proportional to volume, the ratio would be (15/25)^3
June 16, 2016

Maths
well, 3/7 + 5/8 * 4/7 = 11/14
June 16, 2016

maths
2(24+84)/3 * 100
June 16, 2016

math
4/3 pi r^3 = 1200 cm^3 r^3 = 900pi cm^3 ...
June 16, 2016

Math
pi r^2 = 9.5 c = 2pi r = 2pi √(9.5/pi) = 10.93 m
June 15, 2016

Calculus
how about some parentheses, so we know what's where? Also, it would be polite to indicate just what it is you want to know. For starters, just enter your expression in the box at wolframalpha.com and it will show you the graph, its derivative and integral, and more. Be ...
June 15, 2016

math
at 1 pm Train 1 had gone 300 miles. Now you know that one train is going 5/4 as fast as the other. see what you can do from here.
June 15, 2016

physics
font is garbled. Try explaining. review dot and cross products
June 15, 2016

math
2 hrs at 50km/hr = 100 km So, how long does it take to go that far at 40 km/hr?
June 15, 2016

math
a 180° rotation (in either direction) just changes the signs of all the coordinates.
June 15, 2016

Algebra
surely you are not saying that those two answers are equivalent. (2±√10)/2 is the correct solution. If you try plugging in 2√10 you will see that it does not do the job.
June 15, 2016

Math
NYC = 10 ~NYC = 90 NYC & 18 = 10 ~NYC & 18 = .70*90 = 63 Knowing that there are 73 18-yr-olds, and that 10 of them are from NYC, ...
June 15, 2016

Math
if the speed of the prop is x, then the jet is 4x. Since distance = speed * time, we have 4x*2 + x * 1/2 = 850
June 15, 2016

math
ok. I assume you want to know what x is. Well, we know that 8.50x < 54-20
June 15, 2016

Math
A √(100^2+185^2+7^2) = 210.4 km B tanθ = 7/√(100^2+185^2) so, θ=1.9°
June 15, 2016

maths
you have the formula, right? So plug in your numbers.
June 15, 2016

maths
1/4 of 16 = 4 1/2 of 16 = 8 after giving those away, he had 4 left. How did you arrive at your answer?
June 15, 2016

Algebra
pay attention to which variables are paired together, and just add up like terms. For example, the cd terms are 4-(-9)+1-1 = 13cd
June 15, 2016

Algebra
just working with the x² terms, we have -3+2-5 = -6x² do the x's and constants the same way.
June 15, 2016

CALCULUS
done two days ago: http://www.jiskha.com/display.cgi?id=1465840275
June 15, 2016

Algebra
the minimum number of pieces assumes no mistakes, so 30x >= 320
June 15, 2016

math
6+2*5
June 15, 2016

math
surely you can list all pairs of digits whose sum is 9. Then just make sure that the 2nd digit is odd, and you're done. Note that the first digit must be even, if the sum is odd. The first in your list will be 27 and you can surely list the others.
June 15, 2016

math
just make sure the values are equal: 1.20x + 0.90*2 = 1.00(x+2)
June 15, 2016

math
In terms of pints used, .30*4 + .20*3 = x(4+3)
June 15, 2016

maths class 6
so, did you do any of what was asked?
June 15, 2016

calculus
42
June 15, 2016

Math
how cub? 9*12*0.60 is one possible answer.
June 15, 2016

math
at time t hours after noon, we have the distance (starting at k km) is z^2 = (k-30t)^2 + (15t)^2 2z dz/dt = -60(k-30t) + 450t dz/dt = (2250t-60k)/(2z) = 15(75t-2k)/z dz/dt=0 when t = 2k/75 so it depends on how far apart the ships were at noon.
June 15, 2016

Math
If n is the smaller, then we have n + 5n-6 = 12
June 14, 2016

maths
25.75 km/l * 7l = 180.25 km
June 14, 2016

maths
so, how many sevenths are there in a whole apple? Eat one, and how many are left?
June 14, 2016

algebra
wrong. y=2, so it should go 2x+4(2)-6 = 0 2x+8-6 = 0 ... and that's "ordered pair", not "repair"
June 14, 2016

math
any book on trig will show this graph, and explain all the above topics. Where do you get stuck?
June 14, 2016

Algebra 1
a little synthetic division shows that it is 2
June 14, 2016

math
2583/3 = 861 so, that is the middle number
June 14, 2016

Math
not unless it does symbolic math. wolframalpha.com is a nice online calculator you can use for this stuff
June 14, 2016

Math
fastest increase rate is where the slope is steepest. That is, you want a maximum for f'(x). That happens where f"(x) = 0 f = 2cos(2x) f" = -8cos(2x) f"=0 when x=π/4, 3π/4 and so on. The slope is negative at π/4, so you want x = 3π/4 A ...
June 14, 2016

Math
did PsyDag's comment not help you? He told you what to do at each step. Can you not turn that into a function? For example, if you add 3 at each step, after x steps, you have added 3x to the initial value.
June 14, 2016

geometry
x and y will be halfway from one end to the other. That is just the average of the two end values.
June 14, 2016

math
7600(1+.15*25) vs 7600(1+.15)^25 Where do I sign up for that interest rate!?!
June 14, 2016

Physics
no diagram, but just convert each vector to x-y coordinates, and then add them up. then convert back to polar form.
June 14, 2016

math trigo
that's alpha, beta, theta If I read you right, we have θ = α+β tanx/tany = x/y prove: sin(α-β) = (x-y)/(x+y) sinθ well, sinθ = sin(α+β) so now we can say we want sin(α-β)/sin(α+β) = (x-y)/(x+y) note that sin(...
June 14, 2016

Math
140/x = 7/11
June 14, 2016

math
T5 + T24 = 50 a+4d + a+23d = 50 a + a+4d+23d = 50 a + a+27d = 50 T1 + T28 = 50
June 14, 2016

Math
draw your number line mark -3 and 3 now count the intervals between the two numbers.
June 14, 2016

math
volume = area of base * length I assume you can find the area of a triangle.
June 14, 2016

Math
how about using real math symbols? f(x) = (2x-2)^2 - 3x^2 + 6 = 4x^2 - 8x + 4 - 3x^2 + 6 = x^2 - 8x + 10 Now you need a perfect square. = x^2-8x+16 + 10-16 = (x-4)^2 - 6
June 14, 2016

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