# Posts by Steve

Total # Posts: 49,726

**Maths**

0.8m/0.5s = 1.6 m/s

*February 2, 2017*

**Math**

so the formats are different. So what? Rearrange them so they are the same! 5x - 4y = -3 3x + y = 5 Now you can manipulate them. Or, since you know that y = -3x+5, use that in the other equation: 5x - 4(-3x+5) = -3 Solve for x, and then get y.

*February 2, 2017*

**Math**

(5/8) / (1 1/4) = 5/8 / 5/4 = 5/8 * 4/5 = 1/2 hour

*February 2, 2017*

**Algebra Square Roots**

you want 39x to have two factors of 3 or 13 That means x=6, giving us ?(39*6) = ?(3*13*3*2) = 3?26 Not sure that's really any simpler.

*February 2, 2017*

**Math**

so why don't you show us what you did? One way is to notice that 14 = 7*2, so if we double the 2nd equation, we get 8x + 14y = 24 12x + 14y = 20 Now if we subtract the equations, the y's cancel out, and we get -4x = 4 x = -1 Now use that in either equation to get y. 8...

*February 2, 2017*

**Math**

1 hour is 60 minutes, so 1/5 hour = 12 minutes 1/4 hour = 15 minutes So, 3 2/5 hr = 180+24 = 204 min 4 3/4 hr = 240+45 = 285 min

*February 2, 2017*

**Math**

a varied directly as b means that there is some constant k such that a = kb That means that a/b = k and is constant. Thus, you want b such that 4/20 = 50/b 4b = 1000 b = 250 Or, since 50 is 12.5 * 4, b = 12.5*20 = 250

*February 2, 2017*

**Math**

That does sometimes happen. If they had $440 in total, then you'd have 14t = 700 t = 50 That seems most likely.

*February 2, 2017*

**Math**

rather than guessing, do the math f = t-20 j = 3f = 3(t-20) = 3t-60 p = 3j = 3(3t-60) = 9t-180 f+t+j+p = 340 Now you can solve the equations, knowing that the sum will be 340. f+t+j+p = t-20 + t + 3t-60 + 9t-180 = 340 14t-260 = 340 14t = 600 t = 300/7 Hmmm. I get a fraction, ...

*February 2, 2017*

**Math**

Just do what you always do when solving for a variable. Move things around till it is all alone x/y = (x+a-b)/z As usual, just cross-multiply to clear the fractions xz = y(x+a-b) xz = xy + y(a-b) xz-xy = y(a-b) x(z-y) = y(a-b) x = y(a-b)/(z-y)

*February 2, 2017*

**maths**

Suppose we let a = math only b = English only c = science only x = math and science only y = math and English only z = English and science only If you draw the Venn diagram, you see that a+b+c = 36 a+x+y+4 = 22 b+y+z+4=21 c+x+z+4=25 Solve those equations and you get x = b-7 y...

*February 2, 2017*

**calculus**

if x<3, x-3 < 0 5/0 = ? but if the denominator is negative, it is -? Let u = x-3 Then you have the limit (y -> 0-) 5/u The limit is unbounded, and it is negative.

*February 2, 2017*

**calculus**

see http://www.jiskha.com/display.cgi?id=1485970773

*February 2, 2017*

**Math**

you have a geometric progression, with a = 1000 r = 1.5 S5 = 1000(1.5^5-1)/(1.5-1) = 13187.5 The answer key is wrong.

*February 2, 2017*

**Math**

there are lots of fractions in between 1/2 and 1: 1/2 < 4/7 < 3/5 < 5/8 < 2/3 < 3/4 < 1

*February 2, 2017*

**Math**

(7/2)/(3/7) = 7/2 * 3/7 = 3/2 or, 1.5 pieces. You let the fractions scare you. I expect you could solve the problem using easier numbers: How many pieces of 2 feet each can I make out of 10 feet of rope?

*February 2, 2017*

**math**

yes, 38<43 so, what is the answer to the question.

*February 2, 2017*

**math**

n/m

*February 2, 2017*

**Grammar**

there is an implied verb at the end: No one likes tropical fish more than [does]. So it is clearly "she" and not "her". This brings up a common mistake. Many people say My mom likes cookies more than me. meaning that mom is very fond of cookies. But what ...

*February 1, 2017*

**6 grade math**

If a hip-hop jump moves a distance of x feet, then his jumps add up (to the right) to 12+x+x-3-(3*3)+16 = 16+2x I have no idea how far it is from A to B, but if you say he ended at 24, then 2x = 8, and a hip-hop jump is 4 ft.

*February 1, 2017*

**math**

hard to say. They scored 69 pts in all three games. They ask about "the winning game". There were two of them. Assuming they meant "the winning games" then they scored 27+24=51 pts. The score in the losing game is irrelevant.

*February 1, 2017*

**Math**

If you say so

*February 1, 2017*

**Help! Calculus**

?(x^2+1) dy/dx - x/(2y) = 0 ?(x^2+1) dy/dx = x/(2y) 2y dy = x/?(x^2+1) dx y^2 = ?(x^2+1) + c y(0)=1, so 1 = 1+c c = 0 y^2 = ?(x^2+1) y = ?(x^2+1)

*February 1, 2017*

**Math**

1 gal = 8 pt so, use 1/8 of 2 cups of concentrate since 2c = 16 floz, you would use 2 fl oz of concentrate

*February 1, 2017*

**math**

each wire has length x, where x^2 = 18^2 + 47^2

*February 1, 2017*

**value**

density is mass/volume

*February 1, 2017*

**algebra 1**

xy = k so, 2*3 = k k = 6 y = 6/x now fill in the table.

*February 1, 2017*

**Algebra II**

Oops. You missed my typo. The slope is -12. y-4 = -12(x-1) y = -12x + 16

*February 1, 2017*

**Algebra II (plz)**

No problem. I was just working on it when you reposted. It had been almost two hours, and your posting was working its way down the page to obscurity, so it was understandable. The nuisances are people who repost every five minutes and expect someone to be monitoring their ...

*February 1, 2017*

**Algebra II (plz)**

see your earlier post

*February 1, 2017*

**Maths**

y-x = 2.38 y = 3x x+y = 6 You only need two of the equations to solve for x and y. As it happens, there is no solution to all three conditions: Using y-x = 2.38 y = 3x 3x-x = 2.38 2x = 2.38 x = 1.19 y = 3x = 5.37 Fails to satisfy x+y=6 or, using y-x = 2.38 x+y = 6 2x = 8.38 x...

*February 1, 2017*

**College Algebra**

distance = time * speed Let b = boat's speed c = current's speed 5(b-c) = 100 2(b+c) = 100 b-c = 20 b+c = 50 I guess you can take it from there, yes?

*February 1, 2017*

**algebra 1**

since you have no values for y, you cannot determine k.

*February 1, 2017*

**College Algebra**

If that is 1/(x+9), then just plug and chug: f(x+h)-f(x) = 1/(x+h+9) - 1/(x+9) = [(x+9)-(x+h+9)]/[(x+h+9)(x+9)] = (-h)/[(x+h+9)(x+9)] That is the difference. The difference quitient is just that divided by h, so it is -1/[(x+h+9)(x+9)]

*February 1, 2017*

**calculus**

lim(4-g(x))/x = So, 4-g(x) must also approach 0, or the limit would be ±?. Thus, lim g(x) = 4 If you meant 4 - g(x)/x then of course, lim g(x) would be 0, by the same logic.

*February 1, 2017*

**calculus**

?(x^2+x) - ?(x^2-x) (?(x^2+x) - ?(x^2-x))(?(x^2+x) + ?(x^2-x)) ------------------------------------ ?(x^2+x) + ?(x^2-x) (x^2+x)-(x^2-x) ------------------------------- ?(x^2+x) + ?(x^2-x) = 2x/(?(x^2+x) + ?(x^2-x)) divide top and bottom by x (?x^2) = 2/(?(1 + 1/x) + ?(1 - 1/x...

*February 1, 2017*

**math**

y = 45+30x

*February 1, 2017*

**Math (please check my answer!!)**

looks correct. You neglected to mention that X is the intersection of the diagonals.

*February 1, 2017*

**Algebra (check answers plz)**

Find the slope of the line that contains the two points (3,2) and (1,-4). slope is ?y/?x = (-4-2)/(1-3) = -6/-2 = 3 Find the slope of the line that contains the points (-2, 4) and (-4, 6) slope is (6-4)/(-4-(-2)) = 2/-2 = -1 >b>Find the equation of the line that passes ...

*February 1, 2017*

**Geometry**

the only biconditional in the list is C. As it happens, it is also the correct choice. >whew<

*February 1, 2017*

**Maths: Surds**

if the length is x and the height is y, we need y/x = (x/2)/y x^2 = 2y^2 x = ?2 y since xy = 100?2 y=10 x=10?2

*February 1, 2017*

**Math**

Just figure the height above the people, and then add 2 meters. Draw a diagram, and it will be clear that if h is the height above the boaters, h cot12° - h cot16° = 50

*February 1, 2017*

**trigonometry**

r=12 C = 2?r 3 rev/min * 24? ft/rev * 1min/60s = 72?/60 = 6?/5 ft/s

*February 1, 2017*

**Math**

just replace x with whatever quantity you have f(p) = 2p-9 f(x+h) = 2(x+h)-9

*February 1, 2017*

**Carpentry**

assuming the plywood is 3/4" thick, then we have to worry about which direction the shelves are laid out. If the 13" width is parallel to the 48" width of the sheet, then discarding the wastage, we get 48/13 x 96/18 = 3.6 x 5.3 or 15 shelves If laid out the ...

*January 31, 2017*

**basic calculus**

since the topic is calculus, I guess they want to show that y' = -(3x^2+2xy)/(x^2+4y)

*January 31, 2017*

**Geometry**

I will assume the octagon is regular, so each side is 3.5/8 = 7/16. Now just divide the octagon into eight isosceles triangles, each with base 7/16 and vertex angle 45°. The area of each triangle is easy to do, and just multiply it by 8.

*January 31, 2017*

**basic calculus**

Just google area of torus. You will need to know the inner and outer radii of the ring, as well as the radius of the metal wire.

*January 31, 2017*

**Precalculus**

Not sure how you can call x and y points, and then use them as values in an expression. Most precal courses don't cover vectors, and even so, the expression is not a valid vector computation. I guess you could use complex numbers for the points, and then they would be x...

*January 31, 2017*

**Precalculus**

Hmmm. You're right. It's 2?/3

*January 31, 2017*

**Math**

no idea. how much did he have left?

*January 31, 2017*

**Math**

(236-150)/9 = 86/9 = 9.6 so, about 10 more days

*January 31, 2017*

**algebra**

(14)(-3y^-4)/(2*5y^-2) = -42y^-4 * y^2/10 = -21/5 y^-2 If I got the wrong interpretation, maybe you can use some more standard notation to try it again. Try using * for multiplication ^n for raising to the nth power and don't forget parentheses if there is more than one ...

*January 31, 2017*

**math**

-2y

*January 31, 2017*

**Math**

first question: do you know what the order of a function is? The term "order" has several meanings. Do you maybe mean degree of a polynomial? If so, then it's the highest power of the variable.

*January 31, 2017*

**math**

well, each bag weighs 1/2 lb. How many halves in 12?

*January 31, 2017*

**help maths**

This should help you out: http://math.stackexchange.com/questions/1154727/how-to-find-the-locus-of-points-in-the-argand-plane-represented-as-follows

*January 31, 2017*

**Math**

don't ask much, do you? No picture, no description. Try googling the relevant key words.

*January 31, 2017*

**Geometry**

You are right. I found that The scaled score is a reliable estimate of the student's ability using the statistical Rasch ... Values can range from 1300 to 3700 So 5616 does seem absurd. Um, gee - here's an idea. Have you checked with your teacher?

*January 31, 2017*

**Math**

If each correct answer was worth 4 points, and the maximum score was 80, then there must have been 20 questions. if he got x right and y wrong, we have, and only attempted 17 of the 20 questions, then x+y = 17 4x-y = 57 5x = 74 Huh? x must be an integer. So Look for a typo. In...

*January 31, 2017*

**math**

v = pi r^2 h that will give the volume in ft^3 Then just convert to gals.

*January 31, 2017*

**math**

I'll do one. You can follow the method on the others. Recall that 1/(x-a)^n requires terms of A/(x-a) + B/(x-a)^2 + ... + N/(x-a)^n Similarly for 1/(x^2+bx+c)^n. You need terms for each power, of the form (Ax+B)/(x^2+bx+c)^k for k=1..n 3x^2/(x-1)^2 (x-2) = A/(x-1) + B/(x-1...

*January 31, 2017*

**mathsssss**

Using the quadratic formula, a = -1/2 (5+?23) b = -1/2 (5-?23) a + 1/b = -3/2 (5+?23) b + 1/a = -3/2 (5-?23) (x-(-3/2 (5+?23)))(x-(-3/2 (5-?23))) = x^2+15x+(9/2) Or, using the roots in terms of a and b, x^2+x+r = (x-(a+1/b))(x-(b+1/a)) = x^2-((a+1/b)+(b+1/a))x + (a+1/b)(b+1/a...

*January 31, 2017*

**Trigonometry**

the problem is equivalent to (sin x)^2 = (cos 3x)^2 sin^2x = (1/2)(-sin^6x + cos^6x - 15sin^2x cos^4x + 15sin^4x cos^2x + 1) 2-2cos^2x = cos^6x-3cos^4x+3cos^2x+1 + cos^6x + 15cos^4x - 15cos^6x + 15cos^6x - 30cos^4x + 15cos^2x + 1 2cos^6x - 18cos^4x + 20cos^2x = 0 2cos^2x (cos^...

*January 31, 2017*

**complex number**

recall that sinh^-1(z) = ln(z+?(z^2+1)) so, find that, and then convert to polar form. Finally, ln z = ln(r e^i?) = ln(r) + i? In this case, z = 1+i z^2+1 = 1+2i = 2.2361 cis 63.4349° ?(z^2+1) = 1.4954 cis 31.7175° = 1.2720 + 0.7862i z+?(z^2+1) = 2.2729 + 1.7862i = 2....

*January 31, 2017*

**Calculus AB**

no, since as x gets large, the constants become irrelevant, and what you have is basically x^2/x^3 -> 0

*January 31, 2017*

**math**

ax- 2 < -4 ax < -2 if x < -1, then a = 2 2x < -2 x < -1

*January 31, 2017*

**math**

that's & nbsp; If the boat's speed is s mi/hr, then since time = distance/speed, 9090/(s+88) + 9090/(s-88) = 66 The solution seems unreasonable. Check for typos. Like repeated digits. Fix the typos and you will get a nicer answer.

*January 31, 2017*

**PLEASE HELP**

use similar triangles (a side view) to find the radius of the slice 2cm up. Then you can find the volume of the frustrum by subtracting the top part from the whole cone.

*January 31, 2017*

**math**

No. Draw a diagram and it will how how far the horizon is at that altitude. Hint - the radius at the horizon makes a right angle at the surface.

*January 31, 2017*

**math**

so, your equations are 5s+4c+8b = 285 12s+6c = 210 7s+10c+3b = 250 Use your favorite method of solution, and see whether you arrive at this solution: http://www.wolframalpha.com/input/?i=%7B%7B5,4,8%7D,%7B12,6,0%7D,%7B7,10,3%7D%7D*%7B%7Bs%7D,%7Bc%7D,%7Bb%7D%7D+%3D+%7B%7B285%7D...

*January 30, 2017*

**Math**

since x/6 = k/y xy = 6k, a constant So, you want y such that 2*12 = x*8 You don't really have to know what k is.

*January 30, 2017*

**Calculus AB**

sorry about the typo. 4-e was from a previous incorrect solution. It should have read 3/e = 1.1036

*January 30, 2017*

**Calculus AB**

clearly 1/e is no kind of approximation for ln3. However, if we use the tangent at (e,1) (with slope 1/e), the line is y-1 = (1/e)(x-e) Then extending the line to x=3, y-1 = 1/e (3-e) y = 3/e So, 3/e is an approximation to ln3. 4-e = 1.1036 ln3 = 1.0986 The estimate is high, ...

*January 30, 2017*

**Algebra**

google is your friend. The following site is about finding the area, but it also shows how to get the lengths of the sides, so you can use that to find the perimeter. https://www.algebra.com/algebra/homework/Surface-area/Surface-area.faq.question.450961.html

*January 30, 2017*

**Algebra - Repost**

(x^a)^b = x^(ab) x^a * x^b = x^(ab) So, (4x^5y^6z)^2 * (5x^9y^12z)^3 = 16x^10y^12z^2 * 125x^27y^36z^3 = 2000 x^37 y^48 z^5 (x^5)^2 = (x^5)(x^5) = x^10, not x^7

*January 30, 2017*

**Pre-Calculus**

cosx = 1 - 2sin^2 x/2 Now you have a quadratic in u=sin x/2 u = 1-(1-2u^2)

*January 30, 2017*

**Math**

No, since all the interior angles are 135 degrees. 60/120 works for hexagons.

*January 30, 2017*

**Math**

well, how many 10p coins in £1? In £20? and each is 6.5g. And there are 1000g in a kg, so, ...

*January 30, 2017*

**math**

9/10 the pumps, 10/9 the time. 3/2 the volume, 3/2 the time. 10/9 * 3/2 = 5/3 the time. 5/3 * 3 = 5 hours

*January 30, 2017*

**Science**

The difference in their speeds is 50-8 = 42 km/hr. That is the speed at which their separation is decreasing or increasing, depending on which train is in front.

*January 30, 2017*

**MATH HELP QUICK PLEASE!!!!**

looks good to me.

*January 30, 2017*

**Math**

See whether this article gives you what you need. http://math.stackexchange.com/questions/1661986/finding-the-least-integer-n-for-a-function-big-o-of-another-function

*January 30, 2017*

**Maths**

the inside dimensions are 2cm less than the outside, so its inside volume is v = (30-2)(20-2)(10-2) = 28*18*8 = ? cm^3

*January 30, 2017*

**alegbra**

for each step, multiply by -2 and add 1.

*January 30, 2017*

**Calculus II**

What's the trouble? I assume you know how to integrate, so you just want to solve ?[1,a] 1/x^3 dx = ?[a,2] 1/x^3 dx -1/2x^2 [1,a] = -1/2x^2 [a,2] -1/2a^2 + 1/2 = -1/8 + 1/2a^2 1/a^2 = 5/8 a^2 = 8/5 a = ?(8/5) Now do a similar integral using x = 1/?y to find b.

*January 30, 2017*

**math help Please?**

500 * 1.05^t

*January 30, 2017*

**Math**

you can play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html

*January 30, 2017*

**MATHS**

4/3^-3 = 4/(1/27) = 4*27 = 108

*January 30, 2017*

**math**

change to radians arc length s = r? Plug in your numbers.

*January 30, 2017*

**draw a flowchart wich genrates frist 50 items of t**

wow! FORTRAN!! Haven't seen that for a while!!!

*January 30, 2017*

**Math**

Try reading what you posted, fix the errors and make it intelligible.

*January 30, 2017*

**math**

Nope. You have ignored the triangle inequality. From the law of cosines, the angle ? between the 13 and 15 sides is 14^2 = 13^2+15^2-2*13*15 cos? ? = 59.5° So, if we let the short side be u = 13i The 15" side is v = 7.62i + 12.92j The median m is then m = (u+v)/2 = (...

*January 30, 2017*

**physics**

sorry. yes and no. see http://www.wolframalpha.com/input/?i=plot+x%3D10%2B5t-5t%5E2,+y%3D5-10t

*January 29, 2017*

**physics**

yes and yes

*January 29, 2017*

**applied calculus**

v = 5-9.8t h = 25+5t-4.9t^2 Now look for when v=0 or h=0

*January 29, 2017*

**Algebra2**

well, g(4) = 16 so, what is f(16)? Or, f(g(4)) = g(4)-3 and that is f(g(4)) or (f?g)(4)

*January 29, 2017*

**Algebra2**

let f (x)=x-3,and g(x)=x^2 find f(g)(4)

*January 29, 2017*

**Calculus**

true, since sin(0) = 0 1+cos(0) = 2 That is, the left limit is 0 The right limit is 2

*January 29, 2017*

**Trigonometry**

draw a diagram. At first sighting, the distance d1 is d1/12000 = tan 10.4° The second distance d2 is d2/12000 = tan 25.6° Since speed is distance/time, s = (d1-d2 ft)/(2 min) That will be in ft/min.

*January 29, 2017*