Wednesday
September 17, 2014

Posts by Steve


Total # Posts: 25,003

math
each line describes the previous line. So, the next line is 311211 BTW, the last entry in your post should have been 111221, making the real next line 312211
July 14, 2014

Math
Draw the triangle. One leg is 1, and the hypotenuse is 4. So, the other leg is √15 the cosine of the angle is √15/4
July 14, 2014

Differential Equations
(x^2+1)dx + x^2y^2dy=0 x^2y^2 dy = -(x^2+1) dx y^2 dy = -(x^2+1)/x^2 dx 1/3 y^3 = -x + 1/x + C ...
July 14, 2014

Algebra
log0.900.6 - log0.850.6 = 1.7 or, since you probably don't have a button for log0.9x, log(0.6)/log(0.9) - log(0.6)/log(0.85) or even log(0.6)(1/log(0.9)-1/log(0.85))
July 14, 2014

Geometry
I didn't see where the solid was a pyramid. Usually a prism is a right prism, so the v = (area of base)*height
July 14, 2014

science
Name it analogously with table salt, which is Sodium Chloride. That -ide suffix indicates that there are just the two elements. Ever heard of the ointment Zinc Oxide? Same deal.
July 14, 2014

math
the x-coordinate is halfway between the two end x-values: (-3 + -8)/2 = -11/2 Do the y-value the same way.
July 14, 2014

math
after n cuts, the thickness is 0.1 * 2^n mm. so, evaluate when n=30.
July 14, 2014

algebra
just solve for t when the height is zero: -16t^2 + 112t + 128 = 0 just a normal quadratic equation.
July 14, 2014

Alegbra
how many times is this going to be posted? Review the point-slope form of a line: a line with slope m, through the point (h,k) has the equation y-k = m(x-h) So, look at the equation above, and read off m and (h,k)
July 14, 2014

Alegbra
The point is clearly (-5,4) Now since the slope is 3/2, a second point is up 3 and right 2.
July 14, 2014

Trigonometry
just figure s(5)-s(1)
July 14, 2014

physics
The tank weighs the same, regardless of its contents. Figure the volume of material, and multiply that by the material's density. :-)
July 14, 2014

physics
figure the volume: .18 * .78 * .44 m^3 now multiply that by the density, in kg/m^3
July 14, 2014

Pre algebra
(5*62 + 50)/6
July 14, 2014

math
let the numbers be x-1,x,x+1 The sum is 3x = 39 so, the middle number is 13
July 14, 2014

Math
log740353607 = log40353607/log7 = 9 so, 40353607 = 7^9
July 14, 2014

math
x = 2^(1/2) since log √x = 1/2 log x, log x = -2 x = 10^-2 lnx = ln(e*(x+1)) x = e*(x+1) ...
July 14, 2014

Physic
1W = 1J/s 1 kwh = 1000 Wh = 1000J/s * 3600s/h
July 14, 2014

Math
(9+1)/(9+1+6)
July 14, 2014

physics
750 + 750 + 625
July 14, 2014

Calculus 2
actually, the integral isn't so bad if you recognize that the integrand is just x^4 + 1/x^4 http://www.wolframalpha.com/input/?i=arc+length+of+x^5%2F10%2B1%2F%286x^3%29+from+3+to+6
July 14, 2014

Physics
well, you have the mass of 1 liter. So, what is the mass of 2 liters? Now just look up the conversion factor for kg to lb. A handy site is http://www.onlineconversion.com/weight_common.htm On the home page there, you can find many other conversion calculators.
July 14, 2014

mqr/117
rewrite f(x) as 5(x + 3/10)^2 + 11/20 and then you can just read off the coordinates of the vertex.
July 13, 2014

Math
you want the set of elements common to your two sets. So, which numbers are in both lists?
July 13, 2014

Math
The number of people taking something is 23+32-9 So, that leaves how many taking nothing?
July 13, 2014

Alegbra
They are perpendicular if the product of their slopes is -1. So, is (-7)(-7) = -1 ?
July 13, 2014

Math
think of the calendar as units of 24 hours So, 5:44 am on day 10 is the same as 29:44 on day 9. So, subtract 14 from 29 and you have 15:44 of the previous day, or 3:44 pm. Or, you could just subtract 24 hours, giving you 5:44 am of the previous day. But you only wanted to ...
July 13, 2014

Alegbra
If you mean y = -3/2 (x+5) you can see easily that y=0 when x = -5. So, that's where the graph crosses the x-axis. Now, since the slope -s -3/2, just mark a second point, 3 down and 2 to the right from there. Join those two points with a line, and that's the graph.
July 13, 2014

math
I'd say that would be 17+3=20 assuming the ladder is laid vertically against the wall -- an unusual placement, to be sure.
July 13, 2014

math
the grade would be 15/5280 = 0.284%
July 13, 2014

Math 221
as with most problems involving fractions, work first with the denominators. They cannot be added or subtracted unless they all have the same denominator. 5/12 + 7/9 The GCD(12,9) = 36. So, what you have is 15/36 + 28/36 Now all the "units" are the same. Just as you ...
July 13, 2014

maths - oops
Err, I mean one leg=2. So half the chord has length √21
July 13, 2014

maths
Draw a diagram, including the radii to the ends of the chord. Draw the radius perpendicular to the chord. You now have two right triangles with one leg=1 and hypotenuse=5. Half the length of the chord is √24.
July 13, 2014

Algebra II
no, since 2x^2+x-15 = (2x-5)(x+3) Just multiply both sides by (2x-5)(x+3) The thing to watch out for is to be sure to note that 5/2 and -3 must be excluded from the domain.
July 13, 2014

mat/117
you want where P < 0 P(x) = 750x(20-x) You know that P=0 when x=0 or 20 Since the graph is a parabola opening downward, P>0 between the roots. So, P<0 if x>20
July 13, 2014

mat/117
translating upward just means add 11 to g.
July 13, 2014

mat/117
f(x) = -5(x - 3/10) + 29/20 If that doesn't tell you the answer, review your forms of quadratics.
July 13, 2014

mat/117
(fg)(x) = f(x)*g(x) = (-6x-1)(4x^2)
July 13, 2014

mat/117
(f+g)(x) = f(x) + g(x) so, just add the two polynomials together.
July 13, 2014

phi 208
life is like a simile.
July 13, 2014

Math
ok. now what?
July 13, 2014

math
Surely this treated in your text. You want A/(v-1) + B/(v+2) = 1/(v-1)(v+2) A(v+2) + B(v-1) = 1 Av + 2A + Bv - B = 1 (A+B)v + (2A-B) = 0v + 1 For those polynomials to be identical, all of the coefficients must match. So, we have A+B = 0 2A-B = 1 solve those and you get A = 1/3...
July 12, 2014

math
You use partial fractions. 1/(v+2)(v-1) = 1/3 (1/(v-1) - 1/(v+2))
July 12, 2014

science
light is reflected from both sides of the glass.
July 12, 2014

algebra
set x=0 and evaluate y. That's the y-intercept. Ax+By=C has slope -A/B because By = -Ax+C y = -A/B x + c/B In this case, A=9 and B=5
July 12, 2014

math
look at your functions. They indicate that the ball rises as time goes on, and never comes back down. h1(t) = 156 - 16t^2
July 12, 2014

MATH
IF UNIT IS 1, HOW ABOUT 9871 ?
July 12, 2014

Math
oops - I plugged in π/2 instead of π. The solution above is correct if the fan is 1/4 of a circle.
July 12, 2014

Math
The fan is a sector of a circle. That means that 198 = 1/2 (x+3)^2 θ Unless you know how much of a circle the fan occupies (that is, what is θ, compared to 2π), there's no way to solve for x. If the fan is a half-circle, θ=π, so 198 = 1/2 (x+3)^2...
July 12, 2014

English
They are all four compound sentences, so there should be a comma after "summer" #1 is probably the best. #2 implies that there is a specific group of people under discussion. #3 and #4 suffer from a mismatch between plural and singular.
July 12, 2014

English
I think #2 is better. The "still" implies that the study is continuing, rather than having been finished in the past. #1 would be ok if it said something like I studied math for ten years, but never really learned it. #1 is still ok as it is, if you are discussing ...
July 12, 2014

English
The problem appears to be math, and yes, the sentences seem to mean the same thing. Now it's time to work on your English. That would be Do the three mean the same? Or, Are the three the same?
July 11, 2014

Alegbra
the slopes are the same, so they are either parallel or the same line. If you multiply the 1st by -3, the constant term is different from 7, so the lines are parallel.
July 11, 2014

Surds
Hmmm. I get √(4x+1)+√(x+3)=2 4x+1 + 2√(4x^2+13x+3) + x+3 = 4 5x = -2√(4x^2+13x+3) 25x^2 = 4(4x^2+13x+3) 25x^2 = 16x^2 + 52x + 12 9x^2 - 52x - 12 = 0 (9x+2)(x-6) = 0 x = -2/9 , 6 But x=6 does not satisfy the original equation, so -2/9 is the only solution.
July 11, 2014

Math
.075x = 600
July 11, 2014

Math
it is the square root of 1500. That is, it is the number which, when multiplied by itself, equals 1500. √16 = 4 because 4*4 = 16 √25 = 5 because 5*5 = 25 √1500 is not a rational number, but it is approximately 38.73 38^2 = 1444 39^2 = 1521 So, you can see ...
July 11, 2014

Math
√1500 so, now what?
July 11, 2014

electric circuit
are the cells in series or in parallel?
July 11, 2014

math
13112221
July 11, 2014

trigonometry
since there's y^2 but no x^2, it's a parabola, opening to the right: 5x = 4y^2 - 3y - 7 x = 4/5 y^2 - 3/5 y - 7/5 x = 4/5 (y^2 - 3/4 y) - 7/5 x = 4/5 (y^2 - 3/4 y + (3/8)^2) - 7/5 - 4/5 * (3/8)^2 x = 4/5 (y - 3/8)^2 - 121/80 so the vertex is at (-121/80,3/8) http://www...
July 11, 2014

math
what tools do you have at your disposal? Have you learned l'Hospital's Rule yet? If so, that's what I'd use. The limit is the same as for the derivatives: (1/2 cos(x)^-1/2 - 1/3 cos(x)^-2/3)(-sinx) / (1/2 sin(x)^-1/2 * cosx) Take that sinx^-1/2 out of the ...
July 11, 2014

math
There are many proofs of this, such as the one here: http://www.wyzant.com/resources/lessons/math/calculus/derivative_proofs/sinx However, it relies on the fact that sinx/x -> 1 as x->0. That is usually proven as given here: http://math.ucsd.edu/~wgarner/math20a/sin%28x%...
July 11, 2014

maths
divide the sum into 5+6+7=18 equal parts of size x. So, 18x = 3600 x = 200 The shares are thus 5*200 = 1000 6*200 = 1200 7*200 = 1400
July 11, 2014

physics
well you know that AxB = -(BxA) So, if they are equal, they are zero. That means the angle is zero or 180. They are parallel.
July 11, 2014

maths
look at what we have: a+b+c+d = 66.5 b = a-2 c = a+1.5 d = c+1.5 Start substituting: a+(a-2)+(a+1.5)+((a+1.5)+1.5) = 66.5 a=16.0 b=14.0 c=17.5 d=19.0
July 11, 2014

PHYSICS
this just algebra I m1*x = m2*3 - m2*x (m1+m2)x = 3m2 x = 3m2/(m1+m2)
July 11, 2014

PHYSICS
think back to your Algebra I. Collect all the vf terms and factor it out.
July 11, 2014

PHYSICS
12t + 1/2 at^2 = 25 12 + at = 0 solve for a. Now you can solve for µ by using the resultant acceleration.
July 11, 2014

PHYSICS
KE = 1/2 mv^2 work is equivalent to energy.
July 11, 2014

PHYSICS
just a note: that's "mu sub-k," not "muse of k" µk Your class must be an oral presentation, if you never saw it written. Anyway, convert mgh=2.0 * 9.8 * 1.5 to KE, 1/2 * 2.0 * v^2 Using that v, and the frictional force of deceleration, figure the ...
July 11, 2014

PHYSICS
mgh + 1/2 mv^2 stays constant, so mgh1 + 1/2 m*2^2 = mg(h1-3) + 1/2 mv2^2 divide out all the m's and you have 9.8*h1 + 2 = 9.8(h1-3) + 1/2 v2^2 2 = -9.8*3 + 1/2 v2^2 v2^2 = 62.8 v2 = 7.92
July 11, 2014

PHYSICS
KE = 1/2 mv^2, so 0.02 = 1/2 * 2 * v^2 ...
July 11, 2014

Phyiscs
that depends on how long it takes.
July 11, 2014

science
How many moles of H2SO4 in 10g? The molarity of the final mix is moles H2SO4 / 0.1 L
July 11, 2014

NS 2
the distance fallen in t seconds is 16t^2. So, when is 16t^2 = 40000? The air speed of 500 mi/hr is irrelevant, since the horizontal speed does not affect the vertical speed.
July 11, 2014

Statistics
The chance that there are no parents is 10/25 * 9/24 * 8/23 * 7/22 * 6/21 = 6/1265 So, the chance that there is at least one parent is 1259/1265
July 11, 2014

math
better review what an integer is...
July 10, 2014

College Algebra
In any case, wolframalpha.com is your friend. It can confirm the results you get through your hard work: http://www.wolframalpha.com/input/?i=%2815x^2-23x-21%29+%2F+%283x-7%29
July 10, 2014

area
w * 2w = 1000 2w^2 = 1000 w^2 = 500 w = 10√5
July 10, 2014

math
y = (x-5)(x^2-2x+1) / (x-7)(x^2+2x+3) = (x-5)(x-1)(x-1) / (x-7)(x^2+2x+3) If 5<x<7, the numerator is positive the denominator is negative So, no real value of x between 5 and 7 satisfies the condition that y > 0 That is, unless I have misinterpreted your somewhat ...
July 10, 2014

math
the discriminant is negative. That means there are no real roots. That means the graph does not cross the x-axis. That means that the value of y never changes sign. so, your job is to justify why that means that y and a have the same sign.
July 10, 2014

Geometry
tan x = 100/50
July 10, 2014

Geometry
x/20 = sin 65° the height is the side opposite the 65° angle. sine is opposite/hypotenuse
July 10, 2014

Another question (math)
while 2 is 67% of 3, that means that 2 is 33% less than 3. 2 is 1 less than 3. 1 is 33% of 3
July 10, 2014

maths
since the ratio of height to shadow-length is the same, h/22 = 100/55
July 10, 2014

math
2 log base2 (x+15) - log base2 x = 6 log(x+15)^2 - logx = 6 (x+15)^2/x = 2^6 (x+15)^2 = 64x x^2+30x+225 = 64x x^2-34x+225 = 0
July 10, 2014

math
4^y = (2^2)^y = (2^y)^2 so, we have a quadratic in 2^y: (2^y)^2 - 7*2^y - 8 = 0 (2^y-8)(2^y+1) = 0 y=3 2^y is never negative, so 2^y+1=0 has no real solution.
July 10, 2014

math
3 log x = 1 + log (4x+5)/ log 2 That dividing logs stuff is quite unusual for introductory log problems. I will solve 3 log x = 1 + log (4x+5) - log 2 x^3 = 10*(4x+5)/2 2x^3-40x-50 = 0 2(x-5)(x^2+5x+5) = 0 and that's easy If you really did mean to divide the logs, then I ...
July 10, 2014

math
10^(2x+1) -7(10^x) -26 = 0 10*10^2x - 7*10^x - 26 = 0 10*10^(2*2log t) - 7*10^(2log t) - 26 = 0 10*10^(4log t) - 7*10^(2log t) - 26 = 0 10*(10^(log t))^4 - 7*(10^(log t))^2 - 26 = 0 10t^4 - 7t^2 - 26 = 0 (10t^2+13))(t^2-2) = 0 t = ±√2 or ±√(13/10) i
July 10, 2014

Physics
If we let +x be eastward, we have <19.98,13.99> or, approximately <20,14> Add that to <0,-10> and the resultant velocity is <20,4> The (eastward) speed with which the boat is crossing the river is 20m/s. Not sure whether I interpreted your language ...
July 10, 2014

math
-39 + 78 - 100 = -61
July 10, 2014

chemistry
Ya got me. However, the topic is discussed here: http://en.wikipedia.org/wiki/Magnetic_quantum_number
July 10, 2014

math
review the significance of the equation (x-h)^2 + (y-k)^2 = r^2
July 10, 2014

trig
If cosθ = 7/25 in QI, then sinθ = 24/25 That means tanθ = 24/7, and you (ahem) know that tan2θ = 2tanθ/(1-tan^2 θ)
July 9, 2014

math
35/n
July 9, 2014

math
you need x ml of solution, and 15-x ml of water (0 mg/ml), so 20x + 0 = 10*15 x = 7.5 Since the concentration is being reduced by a factor of 2, the volume needs to be increased by that factor. 2 * 7.5 = 15
July 9, 2014

math
If the two heights are h1, and h2 after n hours, the height is h(t) = h1 - (h1-h2)/n t Just plug in all those missing numbers that were not in your post. The burn rate is the height difference divided by how long it took to burn away.
July 9, 2014

math
The formula is above. Plug in r=3. We will assume a smooth, rather than a dimpled, surface :-)
July 9, 2014

math
4π(2r)^2 / 4πr^2 = 4 the square of the radius ratio
July 9, 2014

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