Friday

December 9, 2016
Total # Posts: 47,035

**maybe math**

If Reiny is right, then to simplify, -1/8 + 1/8^2 = -8/8^2 + 1/8^2 = -7/8^2 or, 2 ∑ -2^k/8^2 k=0 How's that for simple? And all positive exponents!

*October 28, 2016*

**Math Derivative**

yes. The good old chain rule. It helps to write them as fractions, so things cancel out: dg/dx = dg/dh * dh/dx I know they usually tell you to avoid thinking of derivatives as fractions, but they really are. It's the same with parametric functions, x(t) and y(t) dy/dx = (...

*October 28, 2016*

**Calculus**

a scalar multiple just distributes as in a complex number: a(x+yi) = ax+ayi (1/2)<-3,7> = <(1/2)(-3),(1/2)(7)>

*October 28, 2016*

**Physics**

conserve total angular momentum.

*October 28, 2016*

**Calculus**

well, y' = -2/(3y), so y" = 2/(3y^2) y' = ...

*October 28, 2016*

**Calculus I**

show what you did. This kind of problem always works out that the fencing is divided equally among lengths and widths. So, the entire array will have dimension (50/3) by (50/4) Each pen will be (50/9) by (50/8) Start with 3x+4y = 100 a = xy = x*(100-3x)/4 then find x such that...

*October 28, 2016*

**Math (Confused)**

9*10^3 * 9*10^4

*October 28, 2016*

**Math (Finding Vertical Tangent)**

looks to me like there is a vertical tangent at x = 2pi/3

*October 28, 2016*

**Algebra**

75% is correct. There is a mistake somewhere in the problem or the answer. Could it be that they won 6 and lost 8? That would make the answer 6/14 instead of 6/8.

*October 28, 2016*

**Chem**

1 mole occupies 22.4L at STP so, you will have 17.8*22.4L PV = nRT

*October 28, 2016*

**Algebra**

cost = revenue to break even So, what is the cost for x pencils?

*October 28, 2016*

**Math**

need for what? and how much is a "dash"?

*October 28, 2016*

**Math**

if x mL were lost and replaced, then .80(250-x) + .40x = .72*250

*October 28, 2016*

**Math - forget it**

Oops - my bad. I misread it. Embershy is correct

*October 28, 2016*

**Math**

23/40 - 23/30 = 23(1/40 - 1/30) = 23(3/120 - 4/120) = 23(-1/120) = -23/120 Note above that 23/30 is not 11/15.

*October 28, 2016*

**Math**

.30*8 + 1.00x = .35(8+x)

*October 28, 2016*

**Chemistry**

The total mass of the solution is x where .0910x = 19.0

*October 28, 2016*

**maths**

660 is nowhere close. You want the circumference of a circle. You don't say whether 220 ft is the diameter or the radius, or even the circumference. If the diameter, your new larger circle has diameter 220+6 = 226 If the radius, your new larger circles has diameter 440+6...

*October 28, 2016*

**easy Math**

well width * length = area so, ...

*October 28, 2016*

**easy math**

(6/2)^2

*October 28, 2016*

**algebra**

6.50 per hour means the hourly charge will be 6.50h so, now what do you think?

*October 28, 2016*

**Calculus**

cosh(3x) = cosh(2x+x) = cosh2x coshx + sinh2x sinhx ...

*October 28, 2016*

**BASIC TECH**

How about some English? With the aid of compass and ruler bisect a line of 12 cm. The length of the line does not matter for the construction. Draw the line AB. Open the compass to more than half the length of AB. From A, draw an arc From B, draw an arc The two arcs (if long ...

*October 28, 2016*

**Maths**

x^2-36 and 2x^2-15x+18 so what?

*October 28, 2016*

**MATHS URGENT**

9/u + 4u = -12

*October 28, 2016*

**MATHS URGENT**

ok ok never mind looking at the related questions. 7^(2x-1) = 7^(2x)/7 4*7^(x-1) = 4*7^x/7 so, doing what they suggested, you have u^2/7 + 4u/7 - 1/14 = 0 Think you can handle that?

*October 28, 2016*

**Physics**

v = at and acceleration is m/s^2, not m/s

*October 28, 2016*

**math**

3C-243

*October 28, 2016*

**Math**

since time = distance/speed, 10/(v+5) = 8/(v-5)

*October 28, 2016*

**9th grade algebra (factoring)**

all correct. Good job.

*October 27, 2016*

**math check answers**

how did you arrive at that amount? The monthly interest rate is only .035/12

*October 27, 2016*

**Math**

Add up the total of all the ages. You have for x people, 41(x-2) + 86+84 = 45x

*October 27, 2016*

**math**

x: v*cos(theta) y: v*sin(theta)

*October 27, 2016*

**Physics**

see the related questions below. Think of polar coordinates, and place the starting point at (r,0)

*October 27, 2016*

**Math**

768 = 3*2^8

*October 27, 2016*

**Math**

well, there's no equation, but the derivative of that expression is just 6(x^2+y^2)^5 * (2x + 2yy')

*October 27, 2016*

**Math**

Implicit Differentiation for (x^2+y^2)^6

*October 27, 2016*

**calculus**

see your previous post - in the related questions below

*October 27, 2016*

**math**

x(1 - 1/4 - (3/4)(3/5)) = 3600

*October 27, 2016*

**Math**

Hydrogen

*October 27, 2016*

**Math (Derivative)**

The definition is the limit of f(x+h) - f(x) ----------------- h That is where the subtraction comes in.

*October 27, 2016*

**Math (Derivative)**

uh -- from the definition of the derivative. Better reread it.

*October 27, 2016*

**math**

Oops - my bad. I was looking for volumes. The overlap is the area of the circular base of the cone (pi r^2) and the circular base of the hemisphere (pi r^2). Subtract it twice, once for each solid.

*October 27, 2016*

**math**

surely you have the formulas for finding the volumes of these solids. Just add 'em up. What do you get? Show work if you get stuck.

*October 27, 2016*

**Economics**

If you borrow $1000 from the bank, and the effective annual rate is 9.4% with monthly compounding. How much do you pay after 2 years?

*October 27, 2016*

**ALGEBRA 2**

surely your text has a section on linear programming, where it explains problems just like this one. Assign variables write the constraints define the objective function evaluate at all the vertices of the region.

*October 27, 2016*

**maths**

(4x-5)(x-5)=175

*October 27, 2016*

**Math**

p = y+5 r = 2(p+y) 10y+20p+25r = 13350

*October 27, 2016*

**Math**

you really gotta work on your typing. volume of tank: π/6 * 10^3 cm^3 fill rate: π*20^2*2 cm^3/s now divide to get the time.

*October 27, 2016*

**math**

note the differences. The amount subtracted is 1,2,3,4,...

*October 27, 2016*

**Algebra 1**

It's always a good feeling when that happens.

*October 27, 2016*

**Algebra 1**

yes, except for the typo y = 3/7 x + 38/7

*October 27, 2016*

**Math**

well, each side is 8, so ...

*October 27, 2016*

**Math**

54 - 8*4 = ?

*October 27, 2016*

**Information Systems Technology**

so, first step: make a loop to read the input, and exit when the employee id = -999

*October 27, 2016*

**Math**

in 3 hours, A is 180 miles ahead. B is going 12 mi/hr faster, so how long to make up the 180 miles?

*October 27, 2016*

**Algebra I**

you have two points. The slope is 10/6 = 5/3. Now, using he point-slope form, you have y-3 = (5/3)(x-4) y = 5/3 x - 20/3 + 3 y = 5/3 x - 11/3 Or, solving for y = mx+b 3 = 4m+b -7 = -2m+b and solve for m and b.

*October 27, 2016*

**Math**

Nope - V = k/T

*October 27, 2016*

**Algebra**

well, f(x) = k/x so, plug in your numbers to find k.

*October 27, 2016*

**Geometry Help?**

#1. Nope - 3^2+4^2 = 25 #2. Nope - the hypotenuse is 10, not the leg #3 ok #4 ok #5 nope - look carefully

*October 27, 2016*

**Maths**

well, the altitude is a/2 √3

*October 27, 2016*

**math**

hint: it's x + 2x-13 = 77

*October 27, 2016*

**math**

well, can't you check it to see whether it works?

*October 27, 2016*

**math**

2c + 4(c+3) = 24

*October 27, 2016*

**tri**

40-20 degrees ?? 40°, or 20°, or 40°20' in any case, if the base is b, then sin(θ/2) = (b/2)/320 = b/640

*October 27, 2016*

**Algebra**

You must mean R', which is clearly all the even numbers. So, not C. Look closely.

*October 27, 2016*

**Physics honors**

not sure what unit "a" is. If it's 7 m/s, then since 1'45" = 105 seconds, it should be clear.

*October 27, 2016*

**math**

read up on the birthday problem: the chance that two will share a birthday.

*October 27, 2016*

**Maths**

so, it was solved earlier, using the wrong equation. Fix it and follow the same steps! It works out better this time. Not only is there a single real root, but a single double root!

*October 27, 2016*

**Maths**

see related questions below

*October 27, 2016*

**MATH HELP PLEASE**

depends on the scale, which you have neglected to provide. It is B if the scale is 1cm:50

*October 27, 2016*

**maths**

37.5 = 75/2 = 60 + 30/2 so, tan 37.5 = tan 75/2 = (1-cos75)/sin75 = (1-cos(60+15))/sin(60+15) ... you get the idea

*October 27, 2016*

**Math**

1,2 ok 3,4 wrong pay attention to the minus signs.

*October 27, 2016*

**Math**

you need to ask some specific questions. No one here can review your whole text for you. Probably wouldn't help anyway. If you can't figure it out from your text, you probably won't be able to do it here. Go online and google problems like the ones you have to do. ...

*October 27, 2016*

**Math**

since you have no examples, google the subject - you will find many many solved problems online.

*October 27, 2016*

**Math**

the volume is just the area of the trapezium times its length.

*October 27, 2016*

**math**

1/3 * 36 = ?

*October 27, 2016*

**maths**

consider the angle θ subtended by the arc he has run on a track of radius r. The location of the point at time t is s*t where s is his speed in units of distance/time. If we lay out the track so he started at (r,0) and ran in a counterclockwise direction, then at time t, ...

*October 27, 2016*

**Algebra**

since there is zero cost, what you charge is all profit, right?

*October 27, 2016*

**Computer Science**

display "enter name, number: " read s (name,num) = split(",",s) while (num-- > 0) { display name } use the language of your choice

*October 27, 2016*

**trigonimetry**

The sides of the triangle are 65,69,80 (sums of radii). So, you can probably find the medians given the sides, yes?

*October 27, 2016*

**Math**

s + s-30 + s-30-20 = 220

*October 27, 2016*

**Easy Algebra Equation**

5-2x-12=14 watch those - signs ...

*October 26, 2016*

**Algebra**

if a linear equation, then a line. Any point on the line has coordinates that satisfy the equation.

*October 26, 2016*

**Algebra**

since the coefficients are rational, the roots come in conjugate pairs. So, the roots are 3-i, 3+i, √2, -√2 f(x) = (x-(3-i))(x-(3+i))(x-√2)(x+√2) = (x^2-6x+9+1)(x^2-2) = ...

*October 26, 2016*

**math**

Ali does 3/2 the work, so he'd take 2/3 the time.

*October 26, 2016*

**Maths**

since the largest reading is 20, you have x+20+20 = 3*16 x = 8 for the smallest.

*October 26, 2016*

**Math**

test post, right?

*October 26, 2016*

**Algebra**

75x < 280+40x

*October 26, 2016*

**Calc**

f '(s) = 10s − 4s^3 f(s) = 5s^2 - s^4 + C f(3)=7, so 5*9-81+C = 7 Do the same for the 2nd one, but use both specified conditions to find the constants.

*October 26, 2016*

**Math**

21 = 7*3 ...

*October 26, 2016*

**Algebra**

9z^2-36z+34 = 0 9(z^2-4z+4) = 2 (z-2)^2 = 2/9 ...

*October 26, 2016*

**math**

b(b+4)/2 = 35

*October 26, 2016*

**ab calculus**

v = 4/3 pi r^3 dv/dt = 4 pi r^2 dr/dt now just plug in your numbers and find dr/dt

*October 26, 2016*

**calculus**

well, usually x is east-west and y is north-south, dontcha think? and both are negative, since they are approaching (0,0). dx/dt = -67 dy/dt = -59 The distance z is z^2 = x^2+y^2 2z dz/dt = 2x dx/dt + 2y dy/dt now just plug in z at the desired moment, and then the rest of your...

*October 26, 2016*

**Science**

v = at

*October 26, 2016*

**Calc**

the two spheres are r=5 and r=7 recall that the volume element is dv = r^2 sinθ dr dθ dØ this is easy to check your answer, since you can just directly subtract the inner volume from the outer one.

*October 26, 2016*

**Algebra 1**

yes..

*October 26, 2016*

**Algebra 1**

yes.

*October 26, 2016*

**8th Grade Pre-Algebra**

I saw this one posted earlier, as (2^8 ⋅ 5^−5 ⋅ 19^0)^−2 ⋅ (5^-2/2^3)^4 ⋅ 2^28 = (2^-16 ⋅ 5^10 ⋅ 1)⋅(5^-8 / 2^12) ⋅ 2^28 = 2^(-16-12+28) ⋅ 5^(10-8) = 2^0 ⋅ 5^2 = 1 ⋅ 25 = 25 You need to get your ...

*October 26, 2016*