# Posts by Steve

Total # Posts: 49,539

**Math**

just multiply 4x5 by 1/2 and 5/4: 2x2.5 and 5x6.25

*February 15, 2017*

**Calc**

f(x) = ?[x,x^8] ln(t) dt The 2nd fundamental theorem is really just the chain rule. f'(x) = ln(x^8)*8x^7 - ln(x)*1/x = 8lnx*8x^7 - ln * 1/x = lnx (84x^7 - 1/x) This works because if g(t) = ?lnt dt g'(t) = ln(t) So, f(x) = g(x^8) - g(x) so, f'(x) = g'(x^8)*8x^7...

*February 15, 2017*

**Math**

yes.

*February 15, 2017*

**too-hard probability sir damon/reiny/steve help**

I get 5/14 = 0.3571 Damon's answer above is P(b=2)/P(w?0) = 0.3546 Seems they ought to be the same ...

*February 15, 2017*

**Math**

1. use the Angle Bisector Theorem. 2. The volume of oil is the area of a circular cap times the length. So, the the formula for the area of a circular cap. Then if the oil volume is v, the depth would have been (v/60?)*15 3. Consider the problem in 2D, and draw a rectangle. If...

*February 15, 2017*

**Math**

m(PQS) + x = 180

*February 15, 2017*

**maths**

a(r^4-1)/(r-1) = 30 a + ar^3 = 18 (r^4-1)/((r-1)(1+r^3)) = 5/3 3r^4-3 = 5r^4-5r^3+5r-5 2r^4-5r^3+5r-2 = 0 (r-1)(r-2)(r+1)(2r-1) = 0 r = 1/2, 1, 2, -1 r=1,-1: extraneous solutions r=2: 2,4,8,16,... r=1/2: 16,8,4,2,...

*February 15, 2017*

**math**

ever think of using math notation instead of words? f(x) = 4x for x <= 3 7-x for x > 3 ?[1,7] f(x) dx = ?[1,3] 4x dx + ?[3,7] 7-x dx = 2x^2[1,3] + 7x - x^2/2 [3,7] = [(2*3^2)-(2*1^2)]+[(7*7-7^2/2)-(7*3-3^2/2)] = 16+8 = 24

*February 15, 2017*

**math**

3 log(u^2/v) 3(2logu - logv)

*February 15, 2017*

**math 103**

the lines intersect at (15,20) The new line has slope -3/5, so it is y-20 = -3/5 (x-15) now massage that into the form you want.

*February 15, 2017*

**Math**

not 810, but vh=810*cos42 Read the information that was given to you.

*February 14, 2017*

**math**

With 90 cattle, he has 9/4 as many mouths, so 4/9 as long to eat: about 16 days

*February 14, 2017*

**Pre calculus**

I cannot find a function of the form 80 + a*e^(-kx) which fits more than two of the points, since when x=0, you have 80+a=176, so a=96 and when x=1 you have 80+96e^-k = 169 e^-k = 89/96 k = ln(96/89) = 0.07571 80+96e^(-0.0757x) does not fit any of the other points.

*February 14, 2017*

**Math**

Each inch has 8 1/8-inch parts. So, 3 1/2 inches is 28 times as long. so, ... or, each inch represents 8 feet. so, 3.5 inches is ? feet

*February 14, 2017*

**Math**

terms are separated by + and - signs.

*February 14, 2017*

**math**

If you plug in your numbers here http://davidmlane.com/hyperstat/z_table.html You will see that it is the 87th %ile.

*February 14, 2017*

**Maths**

p+q = 150 3/4 p = 2/5 q I suspect a typo, as the solution is not an integer.

*February 14, 2017*

**Physical Science**

thank you

*February 14, 2017*

**Physical Science**

A delivery man pushes the button to ring the doorbell. Which of the following forms of energy is not involved in this process? electrical sound mechanical gravitational my answer is gravitational

*February 14, 2017*

**Geometry**

You have 4 sides. Add 'em up and subtract from 30 to get the 5th side. Now, how many are equal?

*February 14, 2017*

**Algebra**

a) which two factors of 6 add to 5? b) which two factors of 6 differ by 1? c) which two factors of 6 add to 1?

*February 14, 2017*

**Algebra**

even integers differ by 2, so the three numbers are x, x+2 and x+4. Now you are told that x(x+2) = 11(x+4)-8 Now solve for x.

*February 14, 2017*

**Math Calc**

the range for an angled shot is R = v^2/g sin2? so, plug in your numbers. Remember to convert ft/s to mi/hr.

*February 14, 2017*

**Math - Calculus**

Recall that the vertical height h is h(t) = 6 + (810 sin42)t - 16t^2 so, just solve for t when h=0.

*February 14, 2017*

**Algebra**

C = P if 0 < P <= 100 Now you can do the part where P > 100, right?

*February 14, 2017*

**Math**

No. That is only the numbers between 0 and 15. You are not restricted to positive values.

*February 14, 2017*

**Math**

real numbers that are less than 15 means s<15

*February 14, 2017*

**College Algebra**

see related questions below...

*February 14, 2017*

**Math 115**

In the first 30 minutes you have walked 3 miles. Then, after a total of 40 minutes, you start walking again. So, D(t) = 3 + 1/60 (t-40) if 40 < t <= 65

*February 14, 2017*

**Calculus**

Since the fraction is pointless as written, I assume you meant M = (log(E)-11.4)/1.5 1.5M = log(E)-11.4 log(E) = 1.5M+11.4 E = 10^(1.5M+11.4)

*February 14, 2017*

**Exponential Equation**

the ^ is used for exponents. I think he means 2e^x^2 + e^x = 4 sometimes they use ^x for ?x In either case, the equation seems unlikely. What do you say, Jason?

*February 14, 2017*

**Exponential**

Just use the usual growth formula. It took 388 years, so 24e^(388r) = 4*10^12

*February 14, 2017*

**algebra**

correct. It can't get from -2 to 6 without going through 0 somewhere in between. You also need to mention that f(x) is continuous. That is necessary.

*February 14, 2017*

**Alebra 2**

recall that x = r cos? y = r sin? now just plug in your numbers.

*February 14, 2017*

**Algebra**

?((-12+2)^2+(-19+3)^2)

*February 14, 2017*

**Mathematics**

No way. I don't think you mean "permuted." Maybe a bit more explanation of the problem would make it clearer just what you have in mind.

*February 14, 2017*

**maths**

7/12 as many stories -- 7/12 as long to type them.

*February 14, 2017*

**Math**

You are correct

*February 14, 2017*

**Data**

Number the pairs 11 22 33 44 55 66 Now, the left shoes can be arranged in 6! ways. For each of those ways, there are 6! ways to arrange the right shoes. Of those, there are 5! arrangements with one matching pair 4! with two matches, ... 1! with 6 matches. So, it seems to me ...

*February 14, 2017*

**Grade 6: money and measures**

1.50n + 10.00*floor(n/30) = 450 n = 246.7 Check: 246 games: 246*1.50 + 10*8 = 449.00 Add $1.50 for the 247th game, and that puts him over the top.

*February 14, 2017*

**algebra**

x/15 = cos75

*February 14, 2017*

**math**

(1 1/4)^2 = (5/4)^2 = 25/16 ft^2

*February 14, 2017*

**Vectors Q#2**

Try reading this discussion. It is the same problem, different points. http://math.stackexchange.com/questions/1300484/distance-between-line-and-a-point

*February 14, 2017*

**Math**

13^2

*February 14, 2017*

**Vectors - Maths**

since CD = CB, vector CD = v If we let AD be vector z, then u.z = (x-v).(x+v) = x.x-v.v Since |x| = |v|, that is zero. So, u and z are perpendicular.

*February 14, 2017*

**Dependent and Independent variables**

a. pick some values for x, and then calculate y. b. pick two of the (x,y) pairs and plot them on graph paper. Draw a line through the two points. All of the other points in your table will also lie on this line. If they do not, you have made a mistake. c. x is independent. You...

*February 13, 2017*

**algebra**

w(2w+4) = 48 w(w+2) = 24 4*6 = 24 4*12 = 48 or, you can solve the quadratic.

*February 13, 2017*

**Precalculus**

one way: determine where a perpendicular line intersects each, and find the distance between the two points of intersection. another way: determine the equation of one of the lines, then find the distance to it from a point on the other line, suing the formula d = |Ax+By+C|/?(...

*February 13, 2017*

**math**

c = 5.00 + 1.50t

*February 13, 2017*

**Algebra**

distributive better go back and read up on both topics

*February 13, 2017*

**Geomety**

well, 2?r^2+2?rh = 500 2?rh = 320 So, 2?r^2 = 180 ?r^2 = 90

*February 13, 2017*

**Calculus**

You need to know the slope of the glider's descent. If he drops straight down, there is no triangle. That is, you need to know his horizontal speed. The vertical drop of 50 ft/s is no good by itself.

*February 13, 2017*

**Math**

If the string covers the entire surface area, consider it a bunch of 3-inch circles. Now, you have to know the diameter of the string. If it is 1/20 inch, then there will be 16*20 = 320 loops. So, nail that down, and you can answer the question.

*February 13, 2017*

**calculus**

actually, the above solution applies if y is the position function. Since it is itself a rate, you need the average value of the function. That is ?[7,10] x^3+2x^2+3 dx ----------------------------- = 782.25 10-7

*February 13, 2017*

**Math**

220+45h Note that when h=0, there is just the flat fee. Then add 45 each time h increases by 1.

*February 13, 2017*

**into to algebra**

add up the amount of alcohol in each part. It must equal the alcohol in the final mixture: .15*150 + .70x = .45(150+x)

*February 13, 2017*

**Introduction to negative linear relationships**

d = m Maybe you need to specify a bit more.

*February 13, 2017*

**physics**

general equation x = a sin(b(t-c))+d Since equilibrium is x=0, d=0 x = a sin(b(t-c)) the period is 9, so b = 2?/9 x = a sin(2?/9 (t-c)) If it travels .4 m in a cycle, the amplitude is 0.1, so x = 0.1 sin(2?/9 (t-c)) Now we have a problem. If x(0) = -0.1, that is its minimum ...

*February 13, 2017*

**Algebra**

.20x = 1

*February 13, 2017*

**math**

42 lbs

*February 13, 2017*

**099**

4x - 30 = -3x - 32 add 3x to both sides 7x - 30 = -32 add 30 to both sides 7x = -2 divide by 7 x = -2/7

*February 13, 2017*

**099 math**

1st step: lose the parentheses: 2(2x-7)-16=3(-x-7)-11 4x-14-16 = -3x-21-11 . . .

*February 13, 2017*

**Math**

angle C = 85° (180-52-43) Labeling the sides a,b,c opposite angles A,B,C, you want side b, since angle B is the smallest angle. b/sinB = c/sinC b/sin43° = 50/sin85° Now just solve for b

*February 13, 2017*

**science**

it takes (50-30)/10 = 2 seconds to reach the final velocity. s = 30t + 1/2 t^2 Now just plug in t=2.

*February 13, 2017*

**Calculus**

1. Just use the power rule recall that 1/x^2 = x^-2 2. product and chain rule: y = x^5 (1+x)^5 y' = 5x^4 (1+x)^5 + x^5 * 5(1+x)^4 = 5x^4(1+x)^4 (1+2x) 3. quotient rule. Assuming the usual carelessness with parentheses, y = (4-x^2)/(2x+3) y' = [(-2x)(2x+3) - (4-x^2)(2...

*February 13, 2017*

**Algebra**

the slope-intercept rule is called that for a reason... Q2. y=kx, so y/x=k, a constant. You want y such that y/10 = 24/8

*February 13, 2017*

**Algebra**

huh?? !! 13/16 = 0.8125 h(13/16) = -16(13/16)^2 + 26(13/16) + 5 = 249/16 = 15.5625 or, h(.8125) = -16*.8125^2 + 26*.8125 + 5 = -10.5625+21.125+5 = 15.5625 Too bad you couldn't be bothered to show your work ...

*February 13, 2017*

**Algebra**

don't forget your Algebra I. h(t) is just a quadratic, and the vertex (maximum height) is at t = -b/2a = 26/32 = 13/16 Now use that to find h(13/16)

*February 13, 2017*

**Maths**

Sn = n/2 (A1+An) = 8/2 (6+46)

*February 13, 2017*

**Trigonometry**

4rpm = 16 in/min, so 1 rev = 4in 2?r = 4, so r = 2/? for the 8" wheel, the ratio of radii is 8/(2/?) = 4? So, if its radius is 4? as big, its speed is 1/(4?) as fast, or 16/(4?) = 4/? in/min It makes 1/(4?) * 4 = 1/? rpm Your unknown radius is ok, but I don't see how ...

*February 13, 2017*

**Calculus for Business Administration and social s**

?(432x^12) = ?(8*27*2 x^12) = 6x^4 ?2

*February 13, 2017*

**Maths**

Let the length AM=1. Let C be the midpoint of AM. Draw the line CO. It has radius 1/2 + r. Draw the line MO. It has length 1-r. So, in the right triangle CMO, 1/2^2 + (1-r)^2 = (1/2 + r)^2

*February 13, 2017*

**math**

you know that the length is between 19.5 and 20.5 meters the width is between 2.5 and 3.5 meters So, use the largest and smallest values to get the range of perimeters.

*February 13, 2017*

**Math 115**

45-4.5t

*February 13, 2017*

**Math 115**

I'll do one: C(t) = 45 - (45-27)/4 * 4 - (27-18)/2 * (t-6) = 27 - 9/2 (t-6) = 54 - 9/2 t if 6 < t <= 8 This should give a clue to the other parts...

*February 13, 2017*

**math**

average value is integral divided by the interval width.

*February 13, 2017*

**math**

I'm guessing you meant ?[4,7] (1+x^2) sinx dx or something. Try reposting with better notation. You can also use my notation above at wolframalpha.com to evaluate integrals.

*February 13, 2017*

**math**

not quite clear on your notation, but the distance is the integral of the velocity over the interval.

*February 13, 2017*

**Physics**

recall that KE = 1/2 mv^2 PE = mgh Now just plug in your numbers.

*February 12, 2017*

**Statistics**

visit this site for Z table stuff: http://davidmlane.com/hyperstat/z_table.html

*February 12, 2017*

**Trigonometry**

Good work, but I interpret the wheel size as the diameter. If so, same steps apply, just adjusted for the smaller radius.

*February 12, 2017*

**Stats**

you can play around with Z table stuff here: http://davidmlane.com/hyperstat/z_table.html For this problem, you find that 99.7% of the area lies less than 2.748 ? above the mean.

*February 12, 2017*

**Algebra**

12r+11s = 228 6r+5s = 108 ...

*February 12, 2017*

**Math**

I don't know what you mean by it "didn't work." It just shows that the expression is never positive. (x-2)^2 is a square, so it is always positive So, -(x-2)^2 is never positive. Trying to plug a formula into a request for a proof will never work. The logic ...

*February 12, 2017*

**Math**

= -(x^2-4x+4) = -(x-2)^2

*February 12, 2017*

**Algebra**

x+y = 900 .05x + .08y = 64.50

*February 12, 2017*

**Algebra**

12a+2c = 122 7a+8c = 160 ...

*February 12, 2017*

**science**

Ca comprises 2/3 of the 1.28g CaCO3, or 0.853g So, assuming that all of the calcium is contained in the CaCO3, the 0.853g is 31.37% of the 2.72g pill

*February 12, 2017*

**college math**

The maximum area occurs when the fencing is divided equally among lengths and widths. For all 4 sides fenced, that is a square. In this case, with the length parallel to the wall, we have length=500/2 = 250 and width = 500/2/2 = 125 so the area is 250*125 = 31,250 This is ...

*February 12, 2017*

**math**

try typing the equations yourself; copy/paste does not do well here. You can copy and paste the ? symbol as you go.

*February 12, 2017*

**math**

.13x + .09(x+700) = 239 x = 800 as above.

*February 12, 2017*

**Geometry**

Draw diagonals AC and DF. The hexagon is now divided into a parallelogram (rectangle?) and two congruent triangles. AC and DF can be found using the law of cosines, since all the interior angles are 120 degrees.

*February 12, 2017*

**math**

what you mean is 2 <= x <= 5 This is just a parabola, with vertex at (2,-1). So, clearly, f(2) = -1 is the minimum value. The axis of symmetry is at x = 2, so f(5) will be the max on the interval [2,5], since it is away from the axis.

*February 12, 2017*

**Algebra**

So, why not use a 1? |3y+4|-1 = 0 |3y+4| = 1 3y+4 = 1 3y = -3 y = -1 3y+4 = -1 3y = -5 y = -5/3

*February 12, 2017*

**algorithm**

for i=1 to 5 prompt for marks read marks[i] next i

*February 12, 2017*

**number base help plz**

1234 = 4^2 + 2*4 + 3 = 2*8 + 8 + 3 = 338

*February 12, 2017*

**College calculus**

x = u/(1 + u^3) y = u^2/(1 + u^3) dy/dx = dy/du / dx/du dy/du = u(2-u^3)/(1+u^3)^2 dx/du = (1-2u^3)/(1+u^3)^2 dy/dx = u(2-u^3)/(1-2u^3)

*February 12, 2017*

**Mathematics of finance 1**

see related questions below

*February 12, 2017*

**maths**

bricks: 180*6*50 * 8 = ? tank: Assuming a square base, v = 150*150*40/1000 L

*February 12, 2017*