Wednesday

June 29, 2016
Total # Posts: 41,497

**Math**

just solve for t in -16t^2 + 120t+ 50 = 10 probably the quadratic formula will be helpful.
*April 28, 2016*

**Calculus**

Draw a side view. If the cylinder has radius r, and height h, then r^2+h^2 = 6^2 the volume of the cylinder is thus v = πr^2h = πr^2√(36-r^2) now just find dv/dr=0 and thus the maximum volume's radius.
*April 28, 2016*

**Calculus**

if the squares are of side x, then v = x(12-2x)^2 = 4x^3-48x^2+144x dv/dx = 12x^2 - 96x + 144 = 12(x-2)(x-6) so, v has a max at x=2.
*April 28, 2016*

**Geometry**

if the lateral area is 232pi, then pi rs = 232pi rs = 232 s^2 = r^2+h^2, so s = √(r^2+441) r√(r^2+441) = 232 r = 9.97 So, let's say r=10. Then a = 10√541 = 232.6 If the total area is 232pi, then use the adjusted formula for that.
*April 28, 2016*

**Maths**

the scale is 1cm:5km the area scale is thus 1cm^2:25km^2 multiply that by 405, and you have 405cm^2 : 10125km^2
*April 28, 2016*

**homework**

I assume the axis of rotation is the line y=49. So, the shells have thickness dy, and v = ∫[0,49] 2πrh dy where r = 49-y and h = (7+√(49-y))-(7-√(49-y)) v = ∫[0,49] 2π(49-y)((7+√(49-y))-(7-√(49-y))) dy = 26891.2π you can check...
*April 28, 2016*

**Algebra**

you can't look at the numbers 2,4,6,8,10 and see a common difference? man, you gotta not be trying!
*April 28, 2016*

**Trigonometry**

it is just the graph of csc(x) shifted left by pi/4 see it at http://www.wolframalpha.com/input/?i=csc%28x%2Bpi%2F4%29,+-pi+%3C%3D+x+%3C%3D+2pi
*April 28, 2016*

**Math.**

T4 and T9 are 5 terms apart. So, d=20/5 = 4 T15 = T9 + 6d = 35+6*4 = 59
*April 28, 2016*

**Math**

(x-15)*6 = 48
*April 28, 2016*

**Algebra**

since the denominators are the same, just add numerators. Just as 2/5 + 1/5 = 3/5, -4x/(x+7) - 8/(x+7) = (-4x-8)/(x+7) So, C -2/(x+3) - 4/(x-5) = [-2(x-5) - 4(x+3)]/[(x+3)(x-5) = (-2x+10-4X-12)/[(x+3)(x-5) = (-6x-2)/[(x+3)(x-5) So, A
*April 28, 2016*

**Algebra**

or C,S,U if drawn without serifs, and you don't count the end of a line as an angle.
*April 28, 2016*

**Maths**

1.16x = 1218
*April 28, 2016*

**maths**

86000 * 1.04^4
*April 28, 2016*

**Algebra**

#1 factored, you have (x+3)(x+3)/(x-1) * (x-1)(x-1)/(x-3)(x+3) The (x-1)(x+3) cancels, leaving (x+3)(x-1)/(x-3) so, A #2 The (x-2) cancels, leaving D
*April 28, 2016*

**algebra 1**

you are correct. Although, since formatting is not always clear online, you should say 1/(x-3) so it is not confused with 1/x - 3 which is how 1/x-3 would normally be interpreted.
*April 28, 2016*

**Maths lit grade 11**

#3.1.1: 175*15 + 275*20 + 250*30 = 15625 #3.1.12: each gallon is 3.785 liters, so just multiply #3.1.3: 1 mile = 1609 meters
*April 28, 2016*

**Physics**

2π radians in each circle, so the angular speed is 8π rad/s 2π*0.5 = π meters in each circle, so the linear speed is 4π m/s
*April 28, 2016*

**Math, Pre-Calculus.**

Actually I was wrong earlier, the answer is actually 26 minutes
*April 28, 2016*

**Math, Pre-Calculus.**

No way to tell. All we know is that the distance AC is somewhere between 28 and 154 miles. So, it will take between about 5 and 31 minutes. I suspect you have left something out,
*April 28, 2016*

**Science**

well, the total mass is 540g now do the divisions to get the fractions
*April 28, 2016*

**Algebra**

#1 ok #2 (x+2)/(5x-15) * (10x^2-25x-15) (x+2)/(5(x-3)) * 5(x-3)(2x+1) the 5(x-3) cancels, leaving (x+2)(2x+1) if x≠3
*April 28, 2016*

**College Algebra (pt.3)**

yes, you did it wrong. You left out the t part: 1000 e^.08t = 1750 e^.08t = 1.75 .08t = log(1.75) t = log(1.75)/.08 = 6.99 or, 7 years. surely you didn't think that the money wold almost double in a year and a half at 8%!
*April 28, 2016*

**Algebra**

when dividing, just subtract exponents 4^4/4^6 = 4^(4-6) = 4^-2 = 1/16 or, you could look at it as 4^4/4^6 = 4^4/((4^4)(4^2)) now the 4^4 cancels, leaving 1/4^2 = 1/16
*April 28, 2016*

**College Algebra (pt.2)**

ln(5x-3) = 0 5x-3 = 1 x = 3/5 Your notation is a bit odd. I think you mean log5(x) = 3 x = 5^3 = 125 log2(32) = x 5 = x because 32 = 2^5 log2(3x+1) = 4 3x+1 = 2^4 = 16 x = 5 ^ is usually reserved for exponents, not used in logs.
*April 28, 2016*

**College Algebra**

6^x = 6^(2x-1) x = 2x-1 x = 1 3^x = 1/27 3^x = 3^-3 x = -3 e^(3x) = 10 3x = ln(10) x = ln10/3 = 0.77 50e^(,09t) = 200 e^(.09t) = 4 .09t = ln4 t = ln4/.09 = 15.40 lnx = -0.25 x = e^-.25 = 0.7788
*April 28, 2016*

**Calculus**

lim(√(4+sinx)-2)/(3x) = lim (cosx/(2√(4+sinx)))/3 -> (1/(2√4))/3 = 1/12
*April 28, 2016*

**MATH**

great post!
*April 28, 2016*

**Army school science**

Sorry i was haste in my reply, the answer is actually defined by e=mc^2 unit vector as proven by einstein
*April 28, 2016*

**Army school science**

initial means "at the start" I assume you know what velocity is. So, you are talking about the speed of something at the start of some process.
*April 28, 2016*

**Calculus**

just use the usual distance formula. The distance between (a,b,c) and Ax+By+Cz+D=0 is |Aa+Bb+Cc+D|/√(A^2+B^2+C^2)
*April 28, 2016*

**Algebra**

You can use =/= for not equal. Or, you can find a site with math symbols, and copy/paste the ≠ character. How can you choose both A and C? (x+7) is a common factor, so A is the choice. Similarly, the second one is B. check your math.
*April 28, 2016*

**programming**

cool.
*April 28, 2016*

**Complex Numbers**

you've been posting this over and over. Did you think of google? Many problems posted here have appeared elsewhere. My first hit on google discusses this problem and one similar to it. Scroll down about halfway and you will find what you need. http://math.stackexchange.com...
*April 28, 2016*

**permutations**

there are 3! ways to arrange 3 things.
*April 28, 2016*

**math**

1/2 + 3/8 = ?
*April 28, 2016*

**mathematics-Remainders theorem**

using mod 21, 17^2^1 ~ 16 17^2^2 ~ 4 17^2^3 ~ 16 ... so, if n is odd, 17^2^n ~ 16 mod 21
*April 28, 2016*

**algebra**

x+y+z = 24 2x = z-2 z = x+y Now just solve for x,y,z
*April 28, 2016*

**Math**

12*6*3 ft^3
*April 27, 2016*

**math**

v = 50 * 4pi/3 * 8^3 a = 50 * 4pi * 8^2
*April 27, 2016*

**Math**

s/6 = (s+4)/20
*April 27, 2016*

**Math**

If he started with f foreign and g local stamps, then we have 3f/4 = g-11 3f = 4g-44 4g-3f = 44 so, if g=32, f = 28 But there are lots of other possibilities.
*April 27, 2016*

**Math**

e = d+12 (2/3 e)/(d + e/3) = 5/7 Ethan gave Dakota $10
*April 27, 2016*

**Math**

he drove for 6 hours at 60 mph, or 360 miles 70% of 360 = 252 25% of 108 = 27 360-(252+27) = 81 since time = distance/speed, 252/65 + 27/54 + 81/x = 6 x = 10530/211 ≈ 49.9 mph
*April 27, 2016*

**Honors Algebra 1**

If there are d donations totalling m dollars, then the charity receives t = 2d+m that means the average is a = (2d+m)/d = 2+m/d If the total of donations is exactly 500 as desired, then a(d) = 2 + 500/d
*April 27, 2016*

**Physics Volume question!!!**

since the range is proportional to the square of the initial velocity, if it has increased by a factor 4, the initial velocity has doubled. Since the volume of water stays the same, that means that the area of the opening has been halved.
*April 27, 2016*

**Pre-Calculus**

y = kx 6 = 4k, so k = 3/2 y = 3/2 x
*April 27, 2016*

**PreCalc**

Reiny is right: 42.5, not 37.5 but I'm sure you caught my error. Note how he offset his function by using a phase shift, which has the same effect as changing the sign as I did, since shifting by 1/2 period does that flip: cos(x+pi) = -cos(x)
*April 27, 2016*

**PreCalc**

the max-min value is 50-35=15, so the amplitude is 7.5. The center line is (35+50)/2 = 37.5 y = 7.5 sin(x) + 37.5 y has a max at t=12, and the period is 24 hours, so the minimum k is a t t=0. cos(x) has a max at x=0, so we have -cos(x) and thus y = -7.5 cos(π/12 x) + 37.5...
*April 27, 2016*

**math**

2":4ft = 2":48" = 1:24
*April 27, 2016*

**Math **

lose the apostrophe in one's, unless you also write event's and coin's and cloud's... independent events do not affect each other. So, I'd choose A,D,E
*April 27, 2016*

**Math **

4/35 = .114 = 11.4% However, the sum of your listed colors (and one color is missing and one is duplicated) does not equal 35.
*April 27, 2016*

**prealgebra**

If you mean 6P2 (permutations of 6 things, 2 at a time), then yes, the answer is 6*5 = 30
*April 27, 2016*

**prealgebra**

could be, depending in the value of P. and what does P2 mean?
*April 27, 2016*

**Trig**

since sin^2θ is never more than 1, you need cos^2θ = 0 so, θ = π/2 or 3π/2 or, solving algebraically, sin^2θ = cos^2θ + 1 cos^2θ - sin^2θ = -1 cos(2θ) = -1 θ = π/2 or 3π/2
*April 27, 2016*

**Geometry**

2πr(r+h) = 112π 8π(4+h) = 112π 4+h = 14 h = 10
*April 27, 2016*

**algebra**

slope = -13 now you can plug that into the point-slope form, using either point.
*April 27, 2016*

**Math**

if the length is L, then you know that 1.8L = 18900 so, divide by 1.8 to get L. If the width is in cm, then you will also get L in cm, so divide that by 100 to get L in meters.
*April 27, 2016*

**Math**

the area is 18900/100^2 = 1.89m^2 so, the length is 1.89/1.8 m
*April 27, 2016*

**Algebra**

2(x + 6x) = 420 x = 30
*April 27, 2016*

**Calculus**

just plug and chug f(x) = f(2) + f'(2)(x-2)/1! + ... f(2) = 1/2 f'(2) = -1/x^2 = -1/2^2 = -1/4 f"(2) = 2/x^3 = 1/4 f(3)(2) = -6/x^4 = -3/8 f(4)(2) = 24/x^4 = 3/4 f(x) = 1/2 + (-1/4)(x-2)/1! + (1/4)(x-2)^2/2! + (-3/8)(x-2)^3/3! + (3/4)(x-2)^4/4! + ... = 1/2 - 1/4 (...
*April 27, 2016*

**Calculus**

From 0 to π/2, 4cos(x) is above 8-4x/π, so the area would be ∫[0,π/2] (8-4x/π)-4cos(x) dx = 7π/2 - 4 But there is a second symmetric region between π/2 and π, so the area is double that, or 7π-8 see http://www.wolframalpha.com/...
*April 27, 2016*

**algebra**

Apparently you mean tn = 75^(5n) = (75^5)^n tn+1 = tn * 75^5
*April 27, 2016*

**Math(Radicals)**

2√6 (3√2 - 12) = 6√12 - 24√6 = 12√3 - 24√6
*April 27, 2016*

**maths**

come on - you have the formulas. plug in your numbers. We can check your results. and that's alpha, not alpher.
*April 27, 2016*

**Math**

log(y+3) = log(x^3/(x-2)) y+3 = x^3/(x-2) y = x^3/(x-2) - 3
*April 27, 2016*

**Logs**

assuming base 10, log(3x-13) = log100 - logx log(3x-13) = log(100/x) 3x-13 = 100/x 3x^2 - 13x - 100 = 0 (3x-25)(x+4) = 0 x = 25/3, since x = -4 is not allowed.
*April 26, 2016*

**math**

well, the extra 4 balls added 3.160-2.040 = 1.12g Now you know how much each ball weighs, so you can figure the mass of the box.
*April 26, 2016*

**math**

Since the tank has a cross-section area of 100π in^2, each in^3 of ball raises the water level by 1/(100π) in. So, figure the volume of the ball and multiply.
*April 26, 2016*

**Arithmetic sequence**

so, follow the hint. add them and multiply them.
*April 26, 2016*

**Geometric series**

apparently you have a = 1 r = -1/√2 S20 = a(1-r^20)/(1-r) = 1023/(512(2+√2))
*April 26, 2016*

**Pre-Calculus**

g(x) has two branches, so g^-1(x) = ±√(x-7) in either case, the domain is all x such that x-7 >= 0 just as the range of g(x) is [7,∞)
*April 26, 2016*

**trig**

34 mi/hr * 1hr/60min * 12*5280in/mi * 1rev/(14π in) = 816.33 rev/min
*April 26, 2016*

**math**

Reiny did this. See the related questions below.
*April 26, 2016*

**Math**

There are lots of solutions, such as 1/2*6+8*5*7/4+3*9 = 100 4/8*6+2*5*7/1+9*3 = 100 8/4*7+6*9*3/2+1*5 = 100
*April 26, 2016*

**Algebra Help me Please**

the y-intercept is the constant term the end behavior is y->∞ or y-> -∞, as with all polynomials. the only other features of interest are the x-intercepts. A little synthetic division will reveal those.
*April 26, 2016*

**math**

anyway, since 2/3 of the odd numbers on a regular die are primes, that means that a prime will come up 2/9 of the time.
*April 26, 2016*

**math**

since odds come up 1/3 of the time, I guess it depends on how many of the odd faces are primes. You haven't said how many faces are on the die.
*April 26, 2016*

**Logs**

since logs are only defined on positive numbers, we need x^2+14x > 0 x(x+14) > 0 You know that this parabola crosses the x-axis at -14 and 0, and since it opens up, it is positive everywhere except between the roots. So, the domain is (-∞,-14)U(0,∞)
*April 26, 2016*

**scte**

you forgot the frequency. anyway, once you have that, just plug in v = L di/dt and crank it out.
*April 26, 2016*

**Algebra**

2*6 = 12 (total length of pythons) 21-12 = 9 (amount left for the corn snakes) 9/3 = 3 feet per corn snake c = (21-2*6)/3
*April 26, 2016*

**Math/Precal**

(9^2x)/(27^x-2)=81^3x-4 since 9 = 3^2 and 27 = 3^3, this is 3^(4x) / 3^(3x-6) = 3^(12x-16) 4x-(3x-6) = 12x-16 x+6 = 12x-16 11x = 22 x = 2 check: 9^4/27^0 = 81^2 yep
*April 26, 2016*

**algebra**

if the steamboat's speed is s, then since time=distance/speed, 147/s = 120/(s-9)
*April 26, 2016*

**math**

I have no idea how many times she rolled the die to get the 12 twos, but since 2 only comes up on average 1/6 of the time, she can expect about 16 twos in 100 rolls.
*April 26, 2016*

**Math-check my answers!!!**

you can easily check your work by typing in your expressions at wolframalpha.com It will show how they can be simplified, and much other information as well.
*April 26, 2016*

**math**

0.10 (1+r)^(2016-1948) = 85 (1+r)^68 = 850 1+r = 1.104 r = .104 or 10.4%
*April 26, 2016*

**Math**

B = F+6 (B-22)+(F-22) = (B+F)/2 Try that. Your solution indicates that when they last met, they were 6 and 14. But 6+14 is not half the sum of their ages today.
*April 26, 2016*

**Math**

Two old friends meet. They hadn't seen each other in 22 years. Betty is 6 years older than France's, but neither is older than 50. The sum of their ages when they met is exactly half of their ages today. How old is Betty? B= F+6 B=50-22 =28 F =50 -22=28 B=28+6=34 Betty...
*April 26, 2016*

**Math**

stop guessing, and try the various functions! Just plug in a value for x and see whether the y also matches. -8*2 - 5 = -21 -8*5 - 5 = -45
*April 26, 2016*

**Math**

A? c? d? help meh
*April 26, 2016*

**Math**

nope. check again.
*April 26, 2016*

**Math**

The ordered pairs (2,-21) and (5,-45) are solutions to which of the following equations? y = -8x - 5 y = -8x + 5 <---- my answer y= 8x - 5 y= 8x + 5
*April 26, 2016*

**maths**

(2x+y+7) - (x-y) = (x-y)-2 (x-3y)-(2x+y+7) = (x-y)-2 x=2, y=-3 ...
*April 26, 2016*

**maths**

n/2 (2*2 + (n-1)(5/4)) = 204 n = 17
*April 26, 2016*

**maths**

Figure how many terms there are (n) Sn = n/2 (39+380)
*April 26, 2016*

**maths**

clearly the limit is -0.3
*April 26, 2016*

**maths**

Tn = 5 + 7(n-1) = 7n-2 S38 = 38/2 (2*5 + 37*7)
*April 26, 2016*

**maths**

do you recognize powers of 3?
*April 26, 2016*

**physics**

Let the speed of sound be s. Then the time taken for the splash to be heard is 45/s seconds. That means that the stone fell for 3.12 - 45/s seconds. You know that stone fell 45m, so 5(3.12-45/s)^2 = 45 s = 375 m/s not too close to the expected value of 343 m/s...
*April 26, 2016*