Thursday

April 17, 2014

April 17, 2014

Total # Posts: 21,724

**Math**

y = 1/2 x - 4 has x-intercept at (8,0) 3x - 4y + 4 = 0 has slope 3/4 so, your line is (using point-slope form) (y-0) = (3/4)(x-8)

**math**

if sold at price p, we need the revenue from 90% of the 600 lbs to be 1.60 times the cost of 600 lbs at $5.59: 600(1-.10)p = 600*5.59*1.60 p = $9.94

**Algebra**

if you mean (fg)(x) that would be f(x)*g(x) = (x-11)(2x+12) = 2x^2-10x-132

**College Mathematics**

For any set with n elements, there are 2^n subsets. But A is not a proper subset of itself, nor is Ø, so that leaves just 2^4-2 = 14. By the way, "the number" is singular, not plural.

**Math**

Ya got me On Monday there was 1/2 bag left. That means 7/14 are left. If he is to eat a few more, then that means there are only 7/14 - 5/14 = 2/14 left after Tuesday's chow-down. But, the next largest candy leaves 1/3 of the bag full. 1/3 > 2/14, so eh? is that 1/3 of ...

**math**

I'll use the more common ^ instead of •, which is often used for simple multiplication. 10^5 = 10*10*10*10*10 = 100,000 it's a simple power. 3^2 = 3*3 2^6 = 2*2*2*2*2*2 = 64 and so on.

**algebra - questions**

What, are we playing Jeopardy?

**geometry**

What, no ideas? A simple review of the properties of the named figures should provide the answers. Or at least allow you to eliminate some possibilities.

**Pre-Algebra**

1:20

**GEOMETRY**

I'd say they are 1/66 times the lengths of AB,BC,CA respectively.

**algebra**

Hmmm. What is f(5)? 7 or 8?

**algebra**

as long as no two distinct pairs have the same 1st element, it is a function. So, what do you think?

**Alg/Trig**

well, you know that h/x = tan 39.8° h/(x+51.7) = tan 19.7° Now eliminate x and solve for h: h/tan39.8° = h/tan19.7° - 51.7 1.2h = 2.8h - 51.7 h = 32.3 check my math, but that's the method to my madness.

**Algebra**

Note that each tree costs the same as 2 bushes. Nick can buy 2-6 trees and 0 bushes, or 4-12 bushes and 0 trees. Each tree can be replaced by two bushes, so it's fairly easy to see how to keep within budget by replacing each tree by 2 bushes.

**ap calculus.linear**

earnings = 0.05 A•f A+f is meaningless, since you can't add ft^2 and n. A•f computes the total ft^2 mowed. For various earnings, you'd also need a vector of rates. Not sure how to do that with just vector operations. Say the rates were 0.05, 0.10, 0.07, 0.12,...

**College Algebra**

depends on the configuration of the pens. A longs skinny corral with 4 pens in a row? Or a rectangular corral with a 2x2 arrangement of pens? If the first, then we have two lengths and 5 widths. 2x+5y = 200 area = xy = x(200-2x)/5 = -2/5 x^2 + 40x the vertex of the parabola is...

**algebra**

apparently an = (-1)^n + 1/2^n as in -1/2, 5/4, -7/8 ... but I could be wrong...

**Maths**

.6b + .9g = 3/4 (b+g) .9g = .6b + 12 Now just solve for b and g

**Math**

Look up in your Z table for the upper tail at 20% You can play around with this at http://davidmlane.com/hyperstat/z_table.html where you can set the mean and variance and explore various properties of the normal distribution

**Math**

LCM(a,b) = a*b/GCF(a,b) so, 36 = a(a+6)/6 a^2 + 6a - 216 = 0 (a+18)(a-12) = 0 a = 12 So, the two numbers are 12 and 18

**Math**

60*5 = x(x+5) x^2 + 5x - 300 = 0 x = 15 The two numbers are 15,20

**Math**

if there are n even numbers (starting at 2, and not skipping any), then n/2 (2*2+(n-1)*2) = 420 n = 20 So, the largest is 40

**math**

AD/AB = DE/BC AD/6 = 20/8 AD = 15

**algebra**

factor it and set each factor to zero.

**Algebra**

You can get excellent graphing help at http://rechneronline.de/function-graphs/ You can plot up to three functions at the same time, and set the x- and y- boundaries as desired. I expect that you plotted the points wrong, if it didn't look like a parabola. Your tables look...

**algebra**

6x-4<-34 or 3x+10>10 6x-4<-34 6x < -30 x < -5 or 3x+10>10 3x > 0 x > 0 You can see the solution graphed at http://www.wolframalpha.com/input/?i=6x-4%3C-34+or+3x%2B10%3E10

**algebra**

5r+4 < 5 5r < 1 r < 1/5

**algebra - an attempt**

s = 5rt t = s/(5-r) t = 25r/s t = r^2-5s t = s/(5r^2) I get t=s/(5r) which is not any of the choices listed. If you want to repost using similar notation, maybe we can help more.

**functions**

lots of rules will produce that, but the easiest is f(x) = x-1

**math**

h/150 = sin 45°

**Math-simplify**

(2x/15)^2 / (.15-x/15)(.2-x/15) (4x^2/15^2) / (x^2-5.25x+6.75)/15^2 The 15^2 cancel out, and we have 4x^2/(x^2-5.25x+6.75) 16x^2/(4x^2-21x+27)

**math**

well, there are 5280 ft/mi, so 15*5280 feet

**trigonometry**

better just stick with "trig" One of the first things to do is to learn the special angles with easy trig values: 0,π/6,π/4,π/3,π/2 Knowing those, you will see that sin π/3 = √3/2 You have -√3/2, so that means that your angle is i...

**Math**

original fraction: n/(2n+4) modified fraction: (n+6)/(2n+4+6) = 7/13 13(n+6) = 7(2n+10) 13n+78 = 14n+70 -n = -8 n=8 So, the original fraction was 8/20 and the new value is 14/26 = 7/13

**math**

2/8 * 1/7

**help**

The month must begin on Monday, so there are 2 full weeks ending on Sunday. The 15th is thus the 3rd Monday.

**chemistry**

you know PV=kT solve for V, then use density = mass/volume

**math**

ab:xy = 10:11 So, other sides are in the same ratio ac/xz = 10/11 14/xz = 10/11 xz = 15.4

**Calculus**

we know that ∫cos(u) du = sin(u) ∫tan(u) du = -log cos(u) So, what we get here is (-1/3)sin(2-3x) - (-1/3)(-log cos(5-3x)) = -1/3 (sin(2-3x) + log cos(5-3x)) + C

**Math**

y = a(x-(-1+√5))(x-(-1-√5)) = a(x^2+2x-4) the one passing through (0,-32) is y = 8(x^2+2x-4) Similarly for the other root pair.

**Quick math help**

I only see one variable: x Factored it is -7(x-1)(2x+3)

**Math**

I'd say 8 8 balls and 8 straws for the base 1 ball and 8 straws for the edges

**Math**

well, it would have to be (2x-7)(2x+3)(x-2) = 117 4x^3 - 16x^2 - 5x - 75 = 0 (x-5)(4x^2+4x+15) = 0 ...

**Math**

2/(2/3) = 3 So, 3 people, each with 2/3 extra bag makes 2 extra bags.

**Algebra 2**

The second formula is correct The games played are 32,16,8,4,2,1 a1=32, r = 1/2 and there are 6 rounds played. 32(1 - 1/2^6)/(1 - 1/2) = 32(63/64)/(1/2) = 63

**Math**

2pi(21-14)

**Math**

if the cost is c, then c(d,v) = 8d + 6v c(5,3) = 8*5 + 6*3 = 58

**Math**

if it doubles at a constant rate, it's exponential growth.

**calculus**

check your graph against this one: http://www.wolframalpha.com/input/?i=tan%28x%29+for+5pi%2F3+%3C%3D+x+%3C%3D+3pi

**Algebra 1**

pick any x, say 5, and plug it in: 4*5 + 3y = 14 now solve for y 20 + 3y = 14 3y = -6 y = -2 So, (5,-2) is a solution Now just do some more. You can also pick a y value and then solve for x.

**math**

p - .20p = 56 .80p = 56 p = 70

**math**

1.5/w = 5/19

**Geometry**

Not sure where the typo is, but assuming you meant 7 and not 12, your reasoning is correct. You can do it the way you did, subtracting the larger from the smaller, or you can do |7 - (-15)) = |7+15| = 22 Personally, I prefer subtracting the smaller, but...

**calculus**

for even values of n > 0 f has a min for odd values of n > 1, inflection

**math**

not sure of your notation. try using ^ for exponents, as in x^2 or y^3 If you want a root, try using the special characters √ ∛ ∜ or use fractional exponents: x^1/2 for square root, etc. or, use a recognizable function name such as sqrt(x) cuberoot(x) 4throot...

**Math**

.04x + .03(15000-x) = 550

**math**

h/200 = tan 60°

**math**

94 - 40

**algebra**

2(26+h) < 180

**math**

that would be 28.05/3 kg

**math**

x/32 = 3/4

**math**

check the differences: 3,6,9,12,15 ... Now it should be clear.

**math**

18/12 s/s t^5/t^3 = 3t^2/2

**math**

4y + xy = 2 4y' + y + xy' = 0 y' = -y/(x+4) Now you can use the quotient rule or another implicit differentiation. 4y" + y' + y'^2 + xy" = 0 So, now just plug in (-3,2) to evaluate it there.

**Calc Help :(((((**

why would I want to help so you "can't do the rest"? I'd hope you can do the rest! Anyway, we all know that 1/∞ = 0 (or that the limit if 1/x as x->∞ is zero), so divide both polynomials by the highest power of x in either, to get (a + b/x^2) /...

**Chemistry**

the molecular mass in grams is the mass of mole. For example, since C has mass 12 amu and O has mass 16 amu, one mole of CO2 has mass of 12+2*16 = 44g 1M solution is 1 mole/1 liter

**HELP**

since 4B = A with a carry, B > 2 and A is a multiple of 4. Since 4A plus the carry generates no carry, 4A < 9 or A <= 2 So, I'd say A=2 and B can be 3 or 8, but 4*28 is 3 digits, so we have 23+23+23+23 = 92

**calculus**

r = ln (x+2)/(x-1) (x+2)/(x-1) = e^r x+2 = e^r x - e^r x(2-e^r) = -e^r x = e^r/(e^r-2)

**math**

Since there are 4 colors, even if the 1st 4 marbles are all different, the 5th marble must be the same color as one of them.

**Mat/116**

ummm. all points (x,y) where y=2x-3.

**math**

.035 * 200 = ?

**algebra**

just do the steps normally taken to solve equations -2 < 2x-4 < 4 add 4 throughout to get 2 < 2x < 8 now divide by 2 to get 1 < x < 4

**English**

#2 haven't forgotten (didn't forget would have been correct) The others are ok.

**algebra**

assoc prop of mult. Also, it's commutative, not communicative!

**math**

1.5 * 1.1^n is NOT 1.65^n That's like saying 2*3^2 = 5^2 Also you are saying that 1.5(-1) = .5 The correct algebra is 100=1.5((1.1^(n) - 1))/(1.1-1) 10 = 1.5(1.1^(n) - 1) Now divide by 1.5 20/3 = 1.1^n - 1 23/3 = 1.1^n n = log(23/3)/log(1.1) = 21.37 or 22 if you round up t...

**add maths**

as you know, the vertex of a parabola is at x = -b/2a. In this case, that will be at x = 12/6 = 2. So, find f(2)

**Probability**

Consider the AB combination as a single letter. Then there are 4!=24 ways to arrange the letters AB,C,D,E. Since A-B can be arranged in two ways, there are 2*4! = 48 ways.

**Math**

not sure what "this" refers to. Radicals and linear equations are separate topics. First step: google the terms you are interested in. You will find a wealth of discussions, far beyond you will find here.

**Math**

5040 + .30p = p p = 5040/.7 = $7200

**math**

I'd say 48000 * (.18+.124+.029) / 4 = 3996

**algebra**

-2(2x+9)>-4x+9 -4x-18 > -4x+9 -18 > 9 what do you think?

**Math**

you have correctly determined that y = -(x-2)^2 (x+2) You know the graph crosses the axis at x = -2 and that it just touches the x-axis at x=2 (because of the double root) Since for large negative values of x, all 3 factors are negative, y > 0 for x < -2 So, y < 0 for...

**Physics**

a = (110-77)/16 = 33/16 m/s^2 displacement during that time is s = 77*16 + 33/32 * 16^2 = 1496 m

**Math**

72 = 2^3 3^2 99 = 3^2 11 54 = 2 3^3 LCM(72,99) = 2^3 3^2 11 = 792 LCM(72,54) = 2^3 3^3 = 216

**Algebra**

you are correct as you surely verified, by using the values in the equations ???

**Algebra**

I think you must have meant -13 and 16. If so, then your algebra isn't entirely useless.

**Algebra**

no ideas at all? Let the numbers be x and y Now, what do you know about them?

**Math**

how does the heart shape relate to the circle and square?

**Math**

Eh? 72 - 5(13+2)*5 72 - 5(15)*5 72 - 75*5 72 - 375 -303

**alg 2**

I can only assume you mean (m•n)^-1 = 1/(m•n)

**Maths**

Yeah, it's kind of tricky. Using 6,1 for factors will make things kind of lop-sided, so I'd go with 2 and 3. (5x-2)(x+3) = 5x^2 + 13x - 6 Nope (5x+3)(x-2) = 5x^2 - 7x - 6 Nope I think we're out of luck. The discriminant is 64+120 = 184, which is not a perfect squar...

**Math**

well, 4,000,000 has 6 zeros. 40 has 1 zero. So, if you need to add 5 more zeros, which multiplier has 5 zeros?

**Algebra**

If the 1,2,3 pointers are in amounts of x,y,z, then x+2y+3z = 95 x+y+z = 54 y = x+16 (x,y,z) = (17,33,4)

**math**

33.60/4 * 1000

**algebra**

12n ≤ 15

**Algebra 1**

initial velocity v is zero - it just fell initial height is 16 feet, so h = -16t^2 + 16 So, you want to find t when h=0 (apple hits the ground) -16t^2 + 16 = 0 -16 (t^2-1) = 0 -16(t+1)(t-1) = 0 So, the apple's height is zero when t=1; that is, one second after being dislod...

**Algebra 1**

Ahem. h = -16(2)^2 + 47(2) + 3 You do not have -(16*2)^2, you just have -16 * 2^2 = -16*4 So, h(2) = -64 + 97 = 33 Ball hits the ground when h=0, so -16t^2 + 47t + 3 = 0 -(t-3)(16t+1) = 0 t = 3

**Algebra 1**

your answer is right, but your units are not The volume is 2500 ft^2 * 10 ft = 25000 ft^3 25000 ft^3 * 1gal/(0.134 ft^3) = 186567 gal

**Algebra 1**

If the moat has width m, castle area = 45*60 = 2700 castle+moat area = (45+2m)(60+2m) since there is moat on both sides. moat area = (45+2m)(60+2m)-2700 Now plug in your value for m, and recall that volume is area * depth

**Math**

so, area = x^2 + 4x(v/x^2) = x^2 + 4v/x Now just find when that is a minimum

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