Wednesday
August 20, 2014

Posts by Steve


Total # Posts: 24,340

Trig help
3sinθ = sinθ - 1 I suspect a typo, but as things stand, 2sinθ = -1 sinθ = -1/2 since sin π/6 = 1/2, and sinθ < 0 in QII,QIV, we have θ = π+π/6 and 2π-π/6
May 20, 2014

algebra
No idea at all?
May 20, 2014

math
no; could be a rhombus, a kite, or even a trapezoid.
May 20, 2014

mathhhh!
wherever there is an x, make it a -2: f(-2) = (-2)^2 = (-2)(-2) = 4
May 20, 2014

Science
A person roller skates down a street heading West. What is true about friction in this case? the choices are 1- does not effect the skates 2- pulls the skates eastward 3- pulls the skates downward toward the center of the earth 4- pulls the skates westward my answer is # 4
May 20, 2014

Calculus
secants connect two points on the graph. The slope of the secant is the average rate of change during that interval. The tangents are just secants where the interval has zero length -- their slopes are the instantaneous rates of change. The initial instantaneous rate is just ...
May 20, 2014

Science
thank you
May 20, 2014

Science
If a bowling ball hits a wall with a force of 6 N the wall exerts what force back on the bowling ball? the choices are 0N 3N 6N 12N I think its 6N
May 20, 2014

Algebra, math,
a^6-b^6 = (a^2)^3 - (b^2)^3 = (a^2-b^2)((a^2)^2+(a^2)(b^2)+(b^2)^2) = (a-b)(a+b)(a^4+a^2b^2+b^4) now do the division and you are left with (a-b)(a+b) = a^2-b^2
May 20, 2014

Algebra, math,
since time = distance/speed, 700/(120-x) = 720/(120+x)+2 x = 20
May 20, 2014

Math
try some grouping: c^2(a-b) - a^2(a+b) + b^2(a+1) That pesky 1 at the end makes me think there's a typo. All the terms are degree 3 except that lone b^2. I suspect there may also be a sign mixed up somewhere as well. Are you sure that's the way it is?
May 20, 2014

Science
thank you
May 20, 2014

Science
A 2,500 kg car moves at 15 m/s squared, 15 m/s squared is the ? a-acceleration b- force c- velocity d-speed My answer is speed
May 20, 2014

maths
x = 21/(x-4) just by inspection, since the factors of 21 are 3 and 7, with one 4 less than the other, that's what I'd expect for roots of the equation. x(x-4) = 21 x^2-4x = 21 x^2-4x+4 = 21+4 (x-2)^2 = 25 x-2 = ±5 x = 2±5 That is, 7 or -3 We can't use...
May 20, 2014

maths
you can read the x-intercepts right off the original equation once you expand it to the desired form, the y-intercept is just the value of c. The vertex (turning point) is midway between the x-intercepts. Since the coefficient of x^2 is positive, the parabola opens upward.
May 20, 2014

maths
just solve for t in 520-5t^2 = 0
May 19, 2014

Math
I don't think this is determined. Take a look at http://mathcentral.uregina.ca/QQ/database/QQ.09.07/h/amanda1.html and you can see that depending on how you divide the diagonals, the median can be a variety of lengths.
May 19, 2014

math
correct until the last line. 7x+5(x+30) = 7*75 + 5*105 = 525+525 = $10.50
May 19, 2014

Algebra 1
If the old cloth had side s, the new cloth satisfies (s-2)(s+2) = 780 26x30
May 19, 2014

Math
the solutions are x = (3±√13)/2 pick the values close to those.
May 19, 2014

Physics
and she moves away from him at 3/4 his speed.
May 19, 2014

Calculus- answer check
Since R"=0 at t=2 and t=4, I see two inflection points. R'=0 at t=1 and t=4. Since R' and R" are both zero at t=4 (because of the multiple root there), there is no max/min at t=4. At R"(1)>0, so that's a local minimum. Not sure about the false ...
May 19, 2014

Math
Looks to me like you have a typo. I get 1,11,21,1211,111221,312211,13112221,... or even 1,11,21,1211,3112,211213,312213,...
May 19, 2014

Algebra 1--Please, help me!
well, shoot. How do you graph any function? You pick some values for x, compute the value for y, and plot some points. Then draw a curve through the points. For y = 200/x + 5, start with x=1 and figure a few points. x y 1 205 2 105 3 71.7 4 55 and so on.
May 19, 2014

algebra1
I get C
May 19, 2014

Geometry
The volume of clay is for a cylinder of radius r is pi r^2(0.75) + pi(r^2-(r-.4)^2)h = 206 Since we have r=4.5, h = 14.6 cm The base is easy, and just subtract that from 206 to get the lateral volume. The lateral surface is just 2pi r h
May 19, 2014

Algebra 2
cos(360-x) = cos(x) so, same as cos 60°
May 19, 2014

Math
for y = a cos(kx) period = 2pi/k amplitude = a
May 19, 2014

Algebra
y^2/9 - x^2/16 = 1 so, what are the foci of y^2/a^2 - x^2/b^2 = 1?
May 19, 2014

math Question
(1-3^10)/(1-3) = 29524
May 19, 2014

Algebra
x^2 = 4py where p = -4 So, ...
May 19, 2014

Please help w/ Algebra
because the perimeter is 56, 2w + 2l = 56 l + w = 28 l = 28-w
May 19, 2014

Please help w/ Algebra
If the field has width w, then the length is 28-w. (w-4)(28-w-4) = 91 w^2-28w+187 = 0 w = 11 The field is 11x17 The smaller area is 7x13 = 91
May 19, 2014

math Question
40/160 = r^2, so r=±1/2
May 19, 2014

Science
A person roller skates down a street heading West. What is true about friction in this case? the choices are 1- does not effect the skates 2- pulls the skates eastward 3- pulls the skates downward toward the center of the earth 4- pulls the skates westward my answer is # 4
May 19, 2014

algebra 2
#1 ok #2 is 80 or -80 b? #3 is a: P(2,3,4,5,6) = 5/6
May 19, 2014

Science
If a bowling ball hits a wall with a force of 6 N the wall exerts what force back on the bowling ball? the choices are 0N 3N 6N 12N I think its 6N
May 19, 2014

Algebra 2
If xy is constant, it's inverse If x/y is constant, it's direct Looks like (b) to me (c) is a bogus answer in any case.
May 19, 2014

math
you are correct.
May 19, 2014

math!
15*12 = 180 330-180 = 150 150/14 = 10 remainder 10
May 19, 2014

Multiple Choice
correct
May 19, 2014

Science
the choices are 1- does not effect the skates 2- pulls the skates eastward 3- pulls the skates downward toward the center of the earth 4- pulls the skates westward
May 19, 2014

Science
A person roller skates down a street heading West. What is true about friction in this case?
May 19, 2014

Science
answers to chose from are 0N, 3N, 6N, 12N
May 19, 2014

Science
If a bowling ball hits a wall with a force of 6 N the wall exerts what force back on the bowling ball?
May 19, 2014

math
1260(1-cos20°)
May 19, 2014

Trig
x^2+11^2 = 24^2 now just solve for x
May 19, 2014

maths
1260(sin30°)
May 19, 2014

math
depends. Is the same formula used for tv's and computers? If so, retail = 2*wholesale-75 wholesale = (retail+75)/2 so, plug in a retail price of $550
May 19, 2014

maths
a^-3 = 1/a^3 c^-1 = 1/c, so 1/(c^-1) = c^1 and we have bc/a^3
May 19, 2014

math
4 times the diameter, 16 times the area
May 19, 2014

Precal/trig
cos2a = 1 - 2sin^2(a) = 1 - 2*9/25 ... in this case, it doesn't really matter which quadrant a is in, as sin^2 is always positive. extra credit: which quadrant is 2a in?
May 19, 2014

math help !
Looks like D to me For #2, always check to see how much y changes when x changes by a fixed amount. That will give the slope of the line (the coefficient of the x term). Here, when x changes by +2, y changes by -1. So, the slope will be -1/2 and the function rule will look ...
May 18, 2014

math
Better check B. It's the differences that are constant, not the ratios. A gives an exponential function. Consider y = 2^x when x grows by 1, y doubles. But, if y = mx+b (a linear function) when x grows by 1, y grows by m, and the difference is constant over equal intervals.
May 18, 2014

Calculus
you want to find c. So, since y(1) = 4, plug it in -1/(1^3+c) = 4 -1/4 = 1+c c = -5/4 Now the particular solution is y = -1/(x^3 - 5/4)
May 18, 2014

Calculus
You wan to find c, so plug in the point (-4,-1) which is on this particular solution curve: (-3*16)/(2+4+c) = -1 The way the function is worded makes me suspect a typo. Fix that, and find c for a particular solution.
May 18, 2014

Calculus
or, 2,000,000 = 10,000,000/5, so log 10^7 - log5 = 7-.699 = 6.301
May 18, 2014

Calculus
log2000000 = log 2 + log 10^6 = 6.301
May 18, 2014

help please
intraocular fluid is the answer I think
May 18, 2014

derivative
you can check your results at wolframalpha.com Just type "derivative" or "2nd derivative" and your function. Check to be sure it interprets your input as you intended. Parentheses are your friend. For your function, you correctly extracted the 9/e constant...
May 18, 2014

Calculus
log(1000000x^19) = log(10^6)+log(x^19) = 6 + 19logx assuming logs base 10 :-)
May 18, 2014

Math help
Assuming ã means √, √338-√200+√162 = √169√2 - √100√2 + √81√2 = 13√2-10√2+9√2 = 12√2 Do the other in the same way: extract perfect roots, and combine the other factors under a single √
May 18, 2014

Math help
#1 -4√2+6√72-√32 = -4√2 + 6√36√2 - √16√2 = -4√2 + 36√2 - 4√2 = 28√2 #2 ok #3 12√13-74√2 remember that √8 = 2√2 #4 ok
May 18, 2014

math
correct except for the inconsistent capitalization
May 18, 2014

math
4! The fact that you are asking this question indicates that you are studying permutations. Surely it was explained in the text.
May 18, 2014

math
view it at wolframalpha.com This site will show you how to graph any function you care to enter. Play around some. http://www.wolframalpha.com/input/?i=1%2F3|x|-2+ Be sure to check to see how it interprets your input. It is pretty strict about using parentheses to alter the ...
May 18, 2014

math
If y = -2x^2 + 3, then just use the values of x and calculate the values of y: x y -3 -2(9)+3 = -15 -2 -2(4)+3 = -5 -1 -2(1)+3 = 1 0 -2(0)+3 = 3 1 1 2 -5 3 -15 Plot those points and sketch a smooth curve through them. Your graph should look like the one given by wolframalpha: ...
May 18, 2014

Mathematics
since the circumference of the ball is 2pi*11.5 = 72.26 cm, divide that into 2800cm to see how many times it rolls.
May 18, 2014

Algebra
add 5 to get the next terms.
May 18, 2014

Nice Save, MathMate
!!
May 18, 2014

algebra - typo?
I suspect a typo, since log3(√10+1)+log3(√10+1) = log3(10-1) = log3(9) = 2 the log7 of powers of 2 is not amenable to simplification. Is there a typo? At the very least, the parentheses are not balanced.
May 18, 2014

math
12 = 2^2 * 3 15 = 3*5 18 = 2*3^2 The smallest number which is a multiple of all of those must contain the highest power of each of the listed primes. So, that will be 2^2 * 3^2 * 5 = 180 But, we also want our number to be a perfect square, so we need to have 5^2 in the product...
May 18, 2014

Calculus
Judging from the graph at http://www.wolframalpha.com/input/?i=[3x^13]e^%28%E2%88%927x%29+for+x%3D0..3 I'd say it is concave down in that interval. In fact, since f"(x) = 3x^11 e^-7x (49x^2-182x+156) if the roots are where you say they are, then since the quadratic ...
May 18, 2014

Calculus
concave down where f" < 0 better review your text, where it is surely explained and illustrated. f" < 0 means that the slope is decreasing. So, f is either rising either rising more slowly or falling more quickly. Consider a parabola which opens downward.
May 18, 2014

geometry
gain of what? perimeter will gain 10% area will grow by a factor of 1.1^2 = 1.21, or 21%
May 18, 2014

average and instantaneous rate of change
average is measured over some finite time interval. Instantaneous is not. It is the limit of the average rate, as the measured interval decreases to zero.
May 18, 2014

algerbra
Ethan donates 1/25 of which money? His earnings, the total earned, the total donated, or what?
May 17, 2014

math
you can convert the hours to minutes 14 X 60 = 840 then add the 3 minutes 840 +3 =- 843 then divide 843/3 = 281 then divide by 60 = 4 hours and 41 minutes
May 17, 2014

Math
Simplify the expression 14 to the minus 4 power
May 17, 2014

Math
Simplify the expression (-8x) times 3x squared
May 17, 2014

Math homework help
AG CE FH
May 17, 2014

Math
5+3√2
May 17, 2014

Calculus
the 3.02375 is correct, but you lost a factor of 10^-8 So, what you really have is .03 micrograms
May 17, 2014

Math - Bazinga!
you gotta be kidding. I suggest you pick out one or two of the types of questions that bother you, post your solutions, and we can check and/or critique them.
May 17, 2014

Algebra
.85^4
May 16, 2014

Calc Help Please Again!
the volume is just a stack of thin discs, of thickness dx, and radius y So, the volume is the integral of pi * y^2 dx = pi*(e^2x + 8e^x + 16) all pretty straightforward. C'mon back if you get stuck, and show where.
May 16, 2014

Algebra 1
first, draw the asymptotes. Then pick a few values of x near the vertical asymptotes, so you get a feel for how y behaves in that region. Then pick a few more values a little farther away, and draw the curve, keeping in mind that it will approach the horizontal asymptote on ...
May 16, 2014

trigonometry
tanθ=1/7 means sinθ=1/√50 cos 2θ = 1-2sin^2θ = 1-1/25 = 24/25 tanØ=1/3 means sinØ=1/√10 and cosØ=3/√10 sin2Ø = 2sinØcosØ = 3/5 so, cos2Ø = 4/5 sin4Ø = 2sin2Øcos2Ø = 24/25
May 16, 2014

algebra
not geometric. The ratio between terms changes. What you have is a modified Fibonacci sequence, where for n>=2, T(n+1) = 2*(T(n-1)+T(n))
May 16, 2014

trig
Assuming L is the right angle, the other two angles are complementary cos(N) = sin(90-N) = sin(M) the co- in cosine, cotangent, cosecant means "complementary" as in complementary angle.
May 16, 2014

chemistry
how many moles in 13g of CS2? The equation tells you that it takes 5 times that many moles of C. same for SO2. Figure the moles of C, then take 2/5 that many of SO2. Then go back to grams. Again, figure the moles, and recall that one mole of a gas occupies 22.4L at STP.
May 16, 2014

math(urgent)
well, of course they have two answers. They wanted to know the amount invested at each of two interest rates! So, what don't you understand? They gave you the equation. If P1 is invested at 12% (which is evident from the equation), then the rest of the money (30000-P1) was...
May 16, 2014

geometry
draw a diagram of a vertical cross-section of the cone, and mark off the altitude. You have a right triangle. The radius of the base is found from r/7.5 = cot(70)
May 16, 2014

business and finite calc
28000 is 0.666 std below the mean 35000 is 2.666 std above the mean. Now go to your Z table. Or, you can play around with this stuff at http://davidmlane.com/hyperstat/z_table.html
May 16, 2014

math
I assume you mean y=2^x and y=-2^x plot them just as you would any other functions. Mark off some points on the x-axis, and calculate the y values, then plot the points. x 2^x -2 1/4 -1 1/2 0 1 1 2 2 4 ... -2^x is just -(2^x), so it is below the x-axis, instead of above it. To...
May 16, 2014

physics
the distance s(t) = 12t - t^2 + c for some c. Since s(1) = -10, c=-21, and so s(t) = -21 + 12t - t^2 a = dv/dt = -6t so just plug in t=4 plug in t= 0 and 10 to find where the particle is at each time, then get the displacement by evaluating s(10)-s(0)
May 16, 2014

algebra - typo?
do you mean two numbers a and ar such that a+ar=28 and a*ar = 512? If so, then there's no real solution. Maybe there's something wrong with the way the problem is presented, eh?
May 16, 2014

Algebra
#1 There must be a typo here. Not factorable #2 (x^2-25)(x^2+4) now it should be easy #3 a little tinkering shows that you have (x+3)(x^2-6x+13) again, complex roots.
May 16, 2014

Math - Int Trig
#31 since f'(x) = -3x^2+2 the extrema are at x = ±√(2/3) f' > 0 for -√(2/3) x < √(2/3) so f is decreasing on that interval, and increasing elsewhere. #32 Since f(x) is odd, and the x^3 coefficient is -1, it rises to the left and drops to ...
May 16, 2014

Math - Algebra2
#1 surely you don't have to ask about this one -- the terms get ever larger #2 is simply a geometric series, with |r| < 1, so it converges.
May 16, 2014

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