Saturday

October 10, 2015
Total # Posts: 34,478

**Algebra**

-10+(-2)(-2)(-2)/(-3) = -10+(4)(-2)/(-3) = -10+(-8)/(-3) = -10+(8/3) = -22/3
*September 15, 2015*

**Algebra**

#1 no question #2 is almost right. What about the alternating +/- signs?
*September 15, 2015*

**math**

A: No, if y<0 B: No, same as A C: No, consider (1,3) D: No, same as C E: No. Clearly if x < y^2, 3x<3y^2 None of the above
*September 15, 2015*

**Geometry**

If the circumference (and hence the radius) grows by a factor of 2, the volume grows by a factor of 2^3 = 8.
*September 15, 2015*

**math**

a^3+a^2b+a+b = (a+b)(a^2+1) 9a^3+9a = 9a(a^2+1) So, the first factor is (a+b)/9a 8a^2-8b^2 = 8(a-b)(a+b) Now multiply and you have (a+b)(16a^2) ---------------------- (9a)(8)(a+b)(a-b) = 2a / 9(a-b)
*September 15, 2015*

**math**

8x^3+729 is the sum of two cubes, so it is (2x+9)((2x)^2-(2x)(9)+9^2) = (2x+9)(4x^2-18x+81) That help?
*September 15, 2015*

**Math**

clearly the number was between 311,111 and 314,999 and was rounded to the nearest 10,000 It could not be less than 310,000, because then it would have been something like 306,827 with a zero.
*September 15, 2015*

**Knox fields.**

I suspect a typo, as 1m is the same as 1^2 m
*September 15, 2015*

**physics**

mg(h2-h1) = 50*9.8*500
*September 15, 2015*

**Chemistry**

If your reaction is 4Fe + 3O2 -> 2Fe2O3 then it takes 2 moles of Fe to produce 1 mole of rust. 5.0g of rust is 0.0313 moles So, how many grams of Fe in 0.626 moles?
*September 15, 2015*

**algebra**

Enter your numbers here http://davidmlane.com/hyperstat/z_table.html to get a feel for how this stuff works.
*September 15, 2015*

**algebra**

I think this site will be a big help. http://davidmlane.com/hyperstat/z_table.html It will show you the fraction more than 2 std away, and you can multiply that by 15000 to get your answer.
*September 15, 2015*

**Uniport ( physis)**

h + vt - 4.9t^2 = 0
*September 15, 2015*

**Math**

since time = distance/speed, 55/(20-x) = 90/(20+x)
*September 15, 2015*

**Geometry**

Hmmm. Let's see. r^2 = 5^2+5^2 = 50 The area is πr^2, or 50*3.14159 = 157.09 Looks like C to me. If you try stuff and it seems wrong, you really should post your work, so we can help fix it.
*September 15, 2015*

**Geometry**

The circle is (x-8)^2 + (y-2)^2 = r^2 Plug in your point (3,7) and you have (3-8)^2 + (7-2)^2 = r^2 Now that you have r^2, you know the area is just pi r^2
*September 15, 2015*

**geometry**

the length of the diameter is √((7-1)^2+(-6-2)^2) = 10 Now you can find the circumference, right?
*September 15, 2015*

**geometry**

Do you not read what I said? Find the lengths of two of the sides. If the points really do describe a rectangle, one side will be the length, and the other will be the width. I assume you can find the perimeter from that information!
*September 15, 2015*

**geometry**

find the lengths WX and XY. Twice their sum is the perimeter. Use the distance formula: WX = √((-5-(-3))^2+(4-7)^2) = √(2^2+3^2) = √13 and so on
*September 15, 2015*

**math**

There are 3x boys and 2x girls 3x+2x = 40 Now find x, and thus the boys and girls
*September 15, 2015*

**physics**

is there a question in there somewhere?
*September 15, 2015*

**Algebra**

Let the amounts at 1,6,8% be x,y,z. We have: x+y+z = 5000 .01x + .06y + .08z = 310 x = y Now just solve for x,y,z
*September 15, 2015*

**Math 104**

the 2" wheel turns twice as fast as the 4" wheel, since it has half the circumference.
*September 15, 2015*

**physics**

how long does it take to fall 1.1m? Double that for the hang time, since he also has to rise that same distance.
*September 14, 2015*

**Geometry**

well, just do the rule: (x,y) -> (x-4,y+6), so (-7,-3) -> (-7-4,-3+6) = (-11,3)
*September 14, 2015*

**Math**

division by zero is undefined. Everywhere else, the expression is defined.
*September 14, 2015*

**Math 10**

clearly, a circle of diameter 20 cm
*September 14, 2015*

**Calculus**

(f(x+h) - f(x))/h = ((x+h)-x)/h = h/h = 1 no need even to take the limit, since 1 is constant.
*September 14, 2015*

**Geometry**

Review your length formula. Find the lengths of the sides, and add them up. I'll give you one side, you do the other two. AB = √((5-(-2))^2+(-3-2)^2) = √(7^2+5^2) = √74
*September 14, 2015*

**Math**

well, since P(red)=1/2, you need red/1260 = 1/2
*September 14, 2015*

**Precalculus**

2500 * 2*2/14 rev/min * 7/3 * 12 * π in/rev * 60min/hr * 1mi/(12*5280)in = 59.5 mi/hr
*September 14, 2015*

**math**

If x at 6%, then .06x + .09(4x+29000) = 29910
*September 14, 2015*

**Math**

just keep multiplying by -1/2
*September 14, 2015*

**Geometry**

Did you find <2? If so, then read my last line above. <1 and <2 are supplementary.
*September 14, 2015*

**Geometry**

<2 = x^2-3x <4 = 6x+10 <2 = <4, so x^2-3x = 6x+10 x^2-9x-10 = 0 (x-10)(x+1) = 0 x = 10 or -1 Now you can figure out the angles. Remember that <1+<2 = <3+<4 = 180
*September 14, 2015*

**Math**

S = L(1-r) S/L = 1-r I expect you can now find r...
*September 14, 2015*

**math**

x = 280 + .04y Your equation looks better, but it does not meet the explanation of x and y. Maybe there's a typo.
*September 14, 2015*

**Pre-Cal**

looks good to me.
*September 14, 2015*

**Physics**

.13km / (62.9-48.9)km/hr = 0.00928 hr now make that into seconds
*September 14, 2015*

**geometry**

Draw the diagram of what is given. Clearly the garden is 3x7. So, the dimensions of the entire area of garden+path is 9x13. The area of the path is thus 9*13-3*7
*September 14, 2015*

**5th grade math**

(3x9)+(18+36)/9=33
*September 14, 2015*

**Math**

I would naturally expect it to have the value -4(0)-6
*September 14, 2015*

**Calculus**

√(81x^2 + x)− 9x = (√(81x^2 + x)− 9x)(√(81x^2 + x)+ 9x)/(√(81x^2 + x)+ 9x) = ((81x^2+x)-81x^2)/(√(81x^2 + x)+ 9x) = x/(√(81x^2 + x)+ 9x) = 1/(√(81 + 1/x)+ 9) as x->∞, that becomes 1/(√81+9) = 1/18
*September 14, 2015*

**Calculus**

well, what is t when h=0? h(t) = t(19-1.86t)
*September 14, 2015*

**algebra**

(2/3)(3)+(1/4)(10)+(1/3)(20) ------------------------------- 3+10+20
*September 14, 2015*

**Math**

is there a question in there somewhere?
*September 14, 2015*

**math**

98654433445*876689956e347 = 9.8654433445e10 * 8.76689956e355 = 8.6489... * 10^366
*September 14, 2015*

**Mathematics in science**

#1. only 1 significant digit. Trailing zeros do not count. See http://www.rpi.edu/dept/phys/Dept2/yesterday/APPhys1/sigfigs/sigfig/node152.html #2. is correct
*September 14, 2015*

**math**

4m doesn't matter how deep the water is.
*September 14, 2015*

**Maths**

just multiply the tops and bottoms: x y^2 z^2 ----------------- yz z y add the powers of each variable: x y^2 z^2 ------------ y^2 z^2 Now cancel like factors, and you wind up with just x
*September 14, 2015*

**Calculus 1**

√(x+h)-√x ------------ h (√(x+h)-√x)(√(x+h)+√x) -------------------------- h(√(x+h)+√x) (x+h)-x ------------------- h(√(x+h)+√x) h --------------------- h(√(x+h)+√x) The h's cancel, and you have 1/(&#...
*September 14, 2015*

**Calculus 1**

just use the difference quotient, and recall how to "rationalize" expressions involving roots: √x - a = (√x-a)(√x+a)/(√x+a)
*September 14, 2015*

**Calculus 1**

I guarantee that your text has this very problem in it. It starts out as the limit of √(x+h)-√x ------------ h That's hard to handle, but if you multiply top and bottom by √(x+h)+√x things will drop out nicely when you take the limit.
*September 14, 2015*

**Calculus 1**

The slope of the tangent for any x is f'(x) = 2x-1 So, you want the line y-f(3) = f'(3) * (x-3)
*September 14, 2015*

**Calculus 1**

x^2-3x+10 is never zero, so there are no VAs. You found the roots, where y=0.
*September 14, 2015*

**Calculus 1**

c'mon, guy, this is just Algebra II. vertical asymptotes where the denominator is zero and the numerator is not zero. Horizontal asymptotes where x is huge. When x is huge huge huge, only the highest powers matter. So, toss out everything else in the top and bottom and see...
*September 14, 2015*

**India international, Mathis trigonometry**

Clearly you have a typo, since cosine is never greater than 1. secθ-tanθ = 4 Since we want cosθ at the end, let's change stuff now: 1/cosθ - sinθ/cosθ = 4 (1-sinθ) = 4cosθ 1-2sinθ+sin^2θ = 16-16sin^2θ 17sin^2θ-...
*September 14, 2015*

**Maths**

Why not get rid of the fractions to start with? Just multiply everything by 5: 5(y+4) = 3(x-1) 5y+20 = 3x-3 Now just rearrange stuff.
*September 14, 2015*

**math**

acar? you mean away? 1000m / (2.5 m/s) = 400s
*September 14, 2015*

**Math**

oops. 1/3 pi r^2 h
*September 14, 2015*

**Math**

bottom half is a cone. r=3, h=6 v = 1/2 pi r^2 h Now just plug in the numbers
*September 14, 2015*

**Geometry**

those two quantities are points, not lines. the only difference between them is their location. I think you want the distance between the points. That is, the length of the line segment joining them. That would be √((6-(-4))^2+(1-3)^2) = √(10^2+2^2) = √104 = ...
*September 14, 2015*

**Math**

BA has initial point B. So, you want a ray with initial point B pointing the other way. That would, of course, be BD.
*September 14, 2015*

**Math**

since KP is in both planes, it will be the intersection. You are correct
*September 14, 2015*

**math**

3 reds, 12 total So, P(red,red) = 1/4 * 1/4
*September 14, 2015*

**adv algebra**

surely if you have discussed probability at all, you must have learned that it is always a number between 0 and 1.
*September 14, 2015*

**Word problem**

42
*September 14, 2015*

**math**

Clearly, it is D. You use random samples to estimate properties of the whole population.
*September 14, 2015*

**Math**

If Michael takes x, hours, then 1/x + 1/(x-2) = 1/9 Now just find x, and then x-2.
*September 14, 2015*

**Math**

ok on the first. 9 x (7-16) + 9 9 x (-9) + 9 -81 + 9 -72
*September 14, 2015*

**Math**

If the 7,8,9% amounts are x,y,z, respectively, then we have x+y+z = 23000 .07x + .08y + .08z = 1800 z = x/2 Just solve that for your answers. Trés simples!
*September 14, 2015*

**math**

if you know how the average is calculated, the solution should be clear. If not, then review the steps for the calculation, and just plug in your numbers.
*September 14, 2015*

**math**

half as much as for 4 servings, since 2 is half of 4.
*September 13, 2015*

**Business**

to tutor at the school
*September 13, 2015*

**Business**

Brianna is organizing a group of staff from her engineering company to provide Saturday afternoon tutoring for students at the nearby middle school. In order for her group of staff to remain stable, what is the optimal number of people she should recruit to help? a- 7 b-5 c-3 ...
*September 13, 2015*

**Business**

thank you
*September 13, 2015*

**Business**

Is your work place an example of a primary or secondary group?
*September 13, 2015*

**algebra**

since time = distance/speed, 18/(x+6) + 16/(x-6) = 5 Now just find x.
*September 13, 2015*

**Maths**

I'll do one, you try the other. y = -2x/7 - 6 multiply by 7 to clear the fraction: 7y = -2x - 42 Now move everything to the left side: 2x + 7y + 42 = 0
*September 13, 2015*

**Math**

f+s=33 f+x = 4(s+x) clearly, f > 4x now, since f/s decreases as both grow So, f > 24, meaning s < 7 You want f to be close to 4s now, so try s=6, f=27 In one year, s=7, f=28 Looks like 1 is the smallest value.
*September 13, 2015*

**math - age problem**

v-3 = 3(p-3) v = 2p v+p=18 clearly Vin is 12 and Paul is 6 You can do that without the first condition at all.
*September 13, 2015*

**math**

You want a circle of radius a inside the circle of radius r, so that pi r^2 = 2pia^2 2a^2 = r^2 a = r/√2
*September 13, 2015*

**Pre-calculus- URGENT**

Think of the unit circle (or any circle centered at (0,0) for that matter). At any angle θ, tanθ = y/x r^2 = x^2+y^2 Complex number a+bi is plotted in the x-y plane, so r^2 = 8^2+√3^2 = 64+3 r = √67 tanθ = √3/-8 That is in QIV (where x is ...
*September 13, 2015*

**math**

a^3-b^3 = (a-b)(a^2+ab+b^2) So, using a=x+y and b=x-y (x+y)^3 - (x-y)^3 = ((x+y)-(x-y))((x+y)^2+(x+y)(x-y)+(x-y)^2) = (2y)(x^2+2xy+y^2+x^2-y^2+x^2-2xy+y^2) = (2y)(3x^2+y^2)
*September 13, 2015*

**mathematics**

You want (1+r)^5 = 2 1+r = 2^0.2 r = 2^0.2 - 1
*September 13, 2015*

**Maths urgent**

the interior angles of an n-gon are (n-2)(180)/n So, you have ((2n-2)/(2n)) / ((n-2)/n) = 5/4 Now just solve for n.
*September 13, 2015*

**Math- Algebra**

The tunnel is 7 trains long. So, 8 train lengths must pass through the tunnel in 2 minutes. The speed is thus 8(600m)/(120s) = 40 m/s
*September 13, 2015*

**Tholulwazi**

acceleration of 2m/s^2 means that the velocity increases by 2m/s every second. So, clearly, since v = at, v = (2m/s^2)(10s) = 20m/s Keep track of the units! They will give clues as to the required calculations.
*September 13, 2015*

**Intermediate math**

These are just the difference of 2 cubes. a^3-b^3 = (a-b)(a^2+ab+b^2) So, the first one is x^3y^6-64 = (xy^2)^3 - 4^3 = (xy^2-4)((xy^2)^2+(xy^2)(4)+4^2) = (xy^2-4)(x^2y^4+4xy^2+16) Do the other in like wise. It comes out very simple. You can use wolframalpha.com to check your ...
*September 13, 2015*

**Difficult algebriac word problem**

danged if I know. Can't quite make sens of your strange syntax. and at night it became double, what became double?
*September 13, 2015*

**mathematics**

You have x^2 + (y+f)^2 = f^2-1 These are circles with center at (0,-f). Clearly the radii of these circles are orthogonal to the curves, and that is the family of lines that pass through (0,-f): y+f = mx
*September 13, 2015*

**Math: Geometric Progression**

a+ar+ar^2 = 70 5ar-4a = 4ar^2-5ar GP is 10,20,40 AP is 40,100,160
*September 13, 2015*

**Math**

a - 1/a = 2 a^2-2a-1 = 0 a = 1±√2 Now just square that and you get 8
*September 13, 2015*

**math**

1.2s (1 - 1/5 - 0.4) = 6/5 s (2/5) = 600 12/25 s = 600 s = 1250
*September 12, 2015*

**Algebra 2**

I find it simpler just to clear the fractions (2/3 - x)/(2/3 + x) multiply top and bottom by 3 and you have (2-3x)/(2+3x) Your final answer is clearly wrong, since you have 3x-2 top and bottom, making the value just -1.
*September 12, 2015*

**Algbra 2**

enter your polynomials at http://calc101.com/webMathematica/long-divide.jsp and see all the details of the division. Or, do synthetic division, using the value of -1 for the root.
*September 12, 2015*

**Calculus 1**

These are a bit tedious, but not hard. I'm sure your book has examples just like them. Give it a go, and come back if you get stuck. Show what you did. Just recall that √(1-2(x+h)) - √(1-2x) can be "rationalized" by multiplying top and bottom by &#...
*September 10, 2015*

**Calculus 1**

yes. I forgot that it said "using limits". Sorry. It's just back to basics.
*September 10, 2015*