Tuesday

October 13, 2015
Total # Posts: 34,587

**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*

**Calculus 1**

v(t) = ds/dt, so (a) v(t) = 2t-8 (b) v(t) = -2/t^3 Just plug in your numbers.
*September 10, 2015*

**Maths**

0.375 grams? What, one kernel per bag? Anyway, just multiply to get the total weight needed.
*September 10, 2015*

**math**

sinθ = 2.1/3.8 distance from wall can be found using either x = 3.8 cosθ or x^2 = 3.8^2 - 2.1^2
*September 10, 2015*

**algebraII**

It says "the number is twelve more than one hundred times the hundred digit" The number is 100z+10y+x. So, you want 100z+10y+x = 100z+12 Now plug in your values and solve for x.
*September 10, 2015*

**Math algebra**

Of course you have some idea. Surely you can graph y = 2x+8 Draw that line, but stop at x=-2 Then between x = -2 and x=3, draw the graph of y = 5-2x Then for x beyond 3, draw the graph of y = -2. Just take it slowly and do one step at a time.
*September 9, 2015*

**Algebra**

66/6
*September 9, 2015*

**Physics ( Thickness of a Spherical Shell)**

The volume of the shell and its interior is v = 4/3 πr^3 = 4/3 π * 2^3 = 33.510 cm^3 That means that the mass (volume*density) is m = 33.510cm^3 * 0.5g/cm^3 = 16.755g So, if the interior radius of the shell is r, then the volume of the actual shell material is v = 4/...
*September 9, 2015*

**algebra 2**

find a line that fits the observed data closely. Read up on least-squares fitting.
*September 9, 2015*

**math **

the tickets to a concert cost $10 for the lower level and $5 for the upper level. A total of 35000 tickets were sold for a total amount of 325000. how many lower level tickets were sold.
*September 9, 2015*

**Math**

assuming no leading zeros, there would be 6 * 6 * 5 candidates.
*September 9, 2015*

**Math**

geez. Just replace every y with 5: 4*5^2 = 4*25 = 100
*September 9, 2015*

**algebra**

I get 12/175 How far did you get?
*September 9, 2015*

**Math**

Yes. Could you not check your answer to see whether it fit the equations? That's faster than posting here and waiting for an answer.
*September 9, 2015*

**MATH HELP**

1A 2C 3B 4D
*September 9, 2015*

**Physics**

A solar still is used to make fresh water from salt water by evaporation. Assume that during a summer day that 1000 BTU/ft sq of solar energy falls on the surface of the salt water. Determine how many inches of water are evaporated in 30 days. Assume that 1040 BTUs is needed ...
*September 9, 2015*

**algebra II**

I'd say that since 1g of water is 1mL, you want 30/v = .085/1 v = 353 mL Of course, I might be wrong.
*September 9, 2015*

**math**

If the distance from the airport to the offices is x, then he drove 250-x miles. Since time = distance/speed, (250-x)/45 + x/120 = 3 Now just solve for x
*September 9, 2015*

**Pre-Calc**

that is correct. The question is poorly worded, though.
*September 9, 2015*

**algebra**

Try this: (x+y)(x-y) = 25(x-y) x+y = 25
*September 9, 2015*

**Algebra (PS)**

Reiny, you're forgettin' the vig!
*September 9, 2015*

**college algeb**

∛(3x^2) * √(2x) = 6throot ((3x^2)^2 * (2x)^3) = 6throot(72x^7) √(3+2√2) * √(3-2√2) = √((3+2√2)(3-2√2)) = √(9-8) = 1 6throot(12) / (√3*∛2) = 6throot(12) / 6throot(3^3 * 2^2) = 6throot(12/36) = 1/6throot(3) ...
*September 9, 2015*

**Algebra**

-12/3 * (-8 + (-4)^2 - 6) + 2 -4 * (-8+16-6) + 2 -4 * 2 + 2 -8 + 2 -6 Just follow the usual order of evaluation.
*September 9, 2015*

**science**

well, if the half-life is n years, you want t where (1/2)^(t/n) = 0.03
*September 9, 2015*

**Pre-Calc**

correct
*September 9, 2015*

**Check my answers MATH**

any terminating decimal is rational any repeating decimal is rational So, their product is also rational Hence (D) You got #2 right, so I'm surprised you missed #1.
*September 9, 2015*

**Global school**

since distance = speed * time, you have 2d = (340 m/s)(0.5 s) Now just find d.
*September 9, 2015*

**algebra**

500(48/120)(3/5) = 120
*September 9, 2015*

**Math**

Hard to tell, looking at your text. try using the more usual notation for online text. Something like (3/2)*(3/2) - 5/(10-6) or something for using fractions.
*September 9, 2015*

**Math**

24/8 + 6*9^2 = 489 B looks good to me.
*September 9, 2015*

**Math**

Clearly, a 50cm square stone is the largest that will evenly tile both dimensions. So, how many of those will fit in each direction?
*September 9, 2015*

**pre-calc @Damon**

Good work, Damon, but the slope was in fact -2.
*September 9, 2015*

**Intermediate algebra**

Just like any other equation. Isolate the variable you want. If you had I = 5t, would that be a problem? No. Well, you have I = (pr)t t = I/(pr)
*September 9, 2015*

**PHYSICS**

(28π cm/rev) * (2020 rev/min) = 56560π cm/min
*September 9, 2015*

**Math 10**

the rules for logs work for any base, so assuming base 4 throughout, log(x*(3x-5)) = log(x) + log(3x-5)
*September 9, 2015*

**Science**

Sorry. I guess I missed the list...
*September 9, 2015*

**Math**

A clearly, f(1) = 0 B and f(0) = 3 C So, f(x) = 3 - 3x Since f(0) = 3, the function will be mx+3 Just find m such that m+3 = 0 since f(1) = 0
*September 9, 2015*

**maths**

Divide the fence equally among the lengths and widths. So, the field is 5000x2500
*September 9, 2015*

**Math word problem**

Counting the cents, we have 10(22) + 1(5*22) = ?
*September 9, 2015*

**maths**

recall the distance formula: 2^2 + h^2 = 6^2
*September 9, 2015*

**Math word problem**

10 + 6*10 = 70
*September 9, 2015*

**Geometry**

AD = 2x+8
*September 9, 2015*

**math**

well, just plug in a 5 for each x: f(5) = (5^2+7)/(5^3+5*5) = 16/75
*September 9, 2015*

**math**

If Charles is now c and Seth is s, Charles was Seth's age c-s years ago, so c = 2(s-(c-s)) c+s = 100 Hmmm. I don't get an integer solution. Check my math.
*September 9, 2015*

**Math**

.40x + .18*50 = .24(x+50)
*September 9, 2015*

**math**

1st step might be to change them all to decimals. Then it will be clear.
*September 9, 2015*

**Algebra**

clearly, it is d = 8 - (1/2)w
*September 9, 2015*

**algebra**

yes, -0.4 is between -0.5 and -0.3 Just draw your number line, and mark the points.
*September 9, 2015*

**math**

well, they are both tenths: 3/10 and 5/10 Now you can simplify
*September 8, 2015*

**Math**

4 5/8 = 4 + 5/8
*September 8, 2015*

**Math**

since 1.6 = 16/10, I'd say yes.
*September 8, 2015*

**Math**

Pablo: 0.08 Beth: 10 * 0.08 = 0.8 Li: 1/10 * 0.08 = 0.008
*September 8, 2015*

**math**

r-6 = 6(j-6) r+4 = 4(j+4) Now just solve for r and j.
*September 8, 2015*

**Geometry**

all the angles add up to 180. Since angle ABD is 90, the other two must add up to 90. So, they are complementary angles.
*September 8, 2015*

**Math**

x = y+25 x+y = 49 ow just find x and y, and go from there.
*September 8, 2015*

**algebra**

-1/3 = 0.33333 -1/2 = 0.50 So, a repeating decimal in between could be -0.3337777777... -0.40404040404040... -0.4444444... -0.4988888888.. For a terminating, just delete the ... -0.345 -0.432 and so on
*September 8, 2015*

**algebra**

If the length is x, the width is 1 + x/4 So, 2(x + 1 + x/4) = 32 Now just solve for x and get the width.
*September 8, 2015*

**algebra**

Since the first train coves the same distance in twice the time, it must have half the speed. So, the trains must be going at 48 and 96 mph.
*September 8, 2015*

**Math**

You only have three numbers on the left, so the only possible expressions are (81+19)/25 = 4 81 + (19/25) = not an integer You sure you want a 9 on the right?
*September 8, 2015*

**Math**

The volume of a spherical cap of radius r and height h is v = π/3 h^2(3r-h) = πrh^2 - π/3 h^3 dv/dt = πh^2 dr/dt + 2πrh dh/dt - πh^2 dh/dt = π(2rh-h^2) dh/dt Now just plug in the numbers: π(2*4*2-4) dh/dt = -10 dh/dt = -5/(6π) cm/hr
*September 8, 2015*

**Chemistry**

Well, then, I'd say the order matters.
*September 8, 2015*

**Math**

just find x where 1/6 + 2/7 + 1/3 + x = 1 Hope you love fractions!
*September 8, 2015*

**Math**

So, is √12 = 4 because 12/3 = 4?
*September 8, 2015*

**English**

thank you
*September 8, 2015*

**English**

Read the following sentences from "The Youngest Doll."The aunt thought he was listening for the breathing of the prawn to see if it was still alive, and shefondly lifted his hand and placed it on the spot where he could feel the constant movement of thecreature's...
*September 8, 2015*

**Math**

w/(7 1/4) = 15/(8 1/2) w = 435/34 = 12 27/34 Strange measurements.
*September 8, 2015*

**Algebra**

see related questions below.
*September 8, 2015*

**physics**

a = ∆v/∆t = (6.90-25.6)m/s / (8.38-0)s = (-18.7 m/s)/8.38s = -2.23 m/s^2
*September 8, 2015*

**Science**

and did you do an experiment and collect data?
*September 8, 2015*

**Coding**

just double-click on cmd.exe
*September 8, 2015*

**calculus - My Bad**

I misread the 2nd problem - go with Reiny.
*September 8, 2015*

**calculus**

D(x) = x^2+2x D(C) = C^2+2C = (4x-5)^2 + 2(4x-5) = 16x^2 - 32x + 15 f(x) = 1+√(x+2) f(f) = 1+√(f+2) = 1+√(1+√(x+2)+2) = 1+√(3+√(x+2))
*September 8, 2015*

**Precalc**

C(x) = 4x-5 C(D) = 4D-5 = 4(x^2+2x)-5 = 4x^2 + 8x - 5
*September 8, 2015*

**Algebra**

M >= 10 O >= 3 3M+12O <= 84
*September 8, 2015*

**math**

2*5*3 = 30
*September 8, 2015*

**math**

1&1/2 ≈ 2 2&6/7 ≈ 3 7*2*3 = 42
*September 8, 2015*

**Algebra**

Anyway, if you suspect a geometric series, just divide any term by the preceding term to get the common ratio (1/5) / 1 = 1/5 (1/25) / (1/5) = 1/5 . . .
*September 8, 2015*

**Algebra**

you can't see the common ratio between 1, 5, 25? Hmmm. a = 1 r = 1/5 S = a/(1-r) = 1/(1 - 1/5) = 1/(4/5) = 5/4
*September 8, 2015*

**Algebra**

It is indeed the commutative property of multiplication.
*September 8, 2015*

**Math**

13 hours is 6 hrs less than 19 hours. So, add 6(0.6) to the height.
*September 8, 2015*

**Math**

The nth term is the sum of the first n positive integers. Or, starting with 1, add 1. Then increase the amount added by 1 for each term. That is, the next amounts added are 2,3,4,5,...
*September 8, 2015*

**math**

24 = 2^3 * 3 36 = 2^2 * 3^2 GCF = 2^2 * 3 = 12 21 = 3 * 7 56 = 2^3 * 7 GCF = 7 For the GCF, find the prime factors and their powers. Then multiply the smallest power of each prime that is common to both numbers.
*September 8, 2015*

**Math**

Assuming that leading zeros are not used, there are 34 and 43 The 3-digit ones are 304 340 403 430 So, add them up
*September 8, 2015*

**PreCalc**

the slope is, naturally, tan(7π/6)
*September 8, 2015*

**PreCalc**

that would be y = tan(1.2) x
*September 8, 2015*

**Math**

72 = 8*9 504 = 7*8*9 Does that help?
*September 8, 2015*

**Math**

LCM(16,24,30) = 240 10000/240 = 41.6 So, 42*240 will be the next multiple of 240.
*September 8, 2015*

**Math**

18 = 2 3^2 25 = 5^2 35 = 5 7 So, the LCM is 2 * 3^2 * 5^2 * 7 = 3150 3150*2 = 6300 3150*3 = 9450 I expect that is the largest 4-digit multiple.
*September 8, 2015*

**Mathematics**

ever hear of a 5-12-13 right triangle? No? Ever hear of the Pythagorean Theorem?
*September 8, 2015*

**Math**

(x-84)/(x-156) = 7/4 x = 252 Note that 252 is not the answer to the question.
*September 8, 2015*

**Math**

12000 * 1.023^5
*September 8, 2015*

**Math**

(a+b)^2 = a^2 + 2ab + b^2 So, 5^2 = 2*4 + a^2+b^2 a^2+b^2 = 17 Now do the next, knowing that (a^2+b^2)^2 = a^4 + 2a^2b^2 + b^4
*September 8, 2015*