Tuesday

May 24, 2016
Total # Posts: 40,760

**Calculus**

x+y = 10 p = xy = x(10-x) = 10x-x^2 dp/dx = 10-2x max p at x=5 what a surprise...
*May 17, 2016*

**math**

well, is y/x constant? 40/2 is not 20/5 is xy constant? 2*40 is not 5*20 so, neither direct nor inverse. of course, you could have just tried some values in the various choices to check them...
*May 17, 2016*

**Math**

not sure what tools you have for estimating polynomial roots, but the signs of the quotient from synthetic division tells you that they are all between -2 and 4. Other than that, some numeric method will have to provide better precision.
*May 17, 2016*

**Algebra**

note that each term increases by 5
*May 17, 2016*

**math**

if price is p and cost is c, then normally, p = 1.8c If c increases by 20%, then 1.8c - 1.2c = 0.6c that is, the profit has changed from .8c to .6c, or a decrease of 25%.
*May 17, 2016*

**Math**

7n-3 = 2n+12 7n = 2n+15 5n = 15 n = 3
*May 17, 2016*

**Science**

figure that all the PE has changed to KE
*May 17, 2016*

**math**

for a given perimeter, the largest area is enclosed by a square. That is, all 4 sides are equal...
*May 17, 2016*

**Applied calculus**

you need Fx = 0 and Fy=0 for a max, so -4x^3 + 2y = 0 -4y^3 + 2x = 0 max f=1/2 at x = y = ±1/√2
*May 17, 2016*

**calculus**

z = 1250ln(yx^2)+45(y^2+x)(x^3 -2y)-(xy)^1/2 if x is fixed, dz/dy = 1250/y + 45(2y)(x^3-2y) + 45(y^2+x)(-2) - (1/2)(x)(xy)^(-1/2)
*May 17, 2016*

**calculus**

copy/paste font problems garbled the post
*May 17, 2016*

**calculus**

well, the distance traveled by the boat is found using d = 280 cot25° - 280 cot 65° speed = distance/time
*May 17, 2016*

**Maths**

1/T = 1/60 + 1/30 + 1/15 = 7/60
*May 17, 2016*

**maths**

1991 is 4 years from 1987, so the projection is (in billions) 5 * 1.02^4
*May 17, 2016*

**Math**

multiply the ratio by 9 and you have 45:18
*May 17, 2016*

**math**

using similar triangles, you can see that PH/4 = 18/PH PH^2 = 72 PH^2 + PF^2 = 18^2 PL/4 = PF/PH
*May 17, 2016*

**Percent of loss**

523.20 * .192 = ?
*May 17, 2016*

**Geometry**

multiply the ratio by 24/5 and you have 72/5 : 24 or 14.4:24
*May 16, 2016*

**science**

you are reducing the molarity by a factor of 3, so you need to increase the volume by a factor of 3. 1/3 acid and 2/3 water don't add the acid to the water!
*May 16, 2016*

**Algebra**

it lands when h=0. So, just solve the quadratic the way you do normally.
*May 16, 2016*

**science**

how long does it take to fall? 4.9t^2 = 30 now use v = 9.8t to get the speed.
*May 16, 2016*

**Physics**

it might be, but probably not.
*May 16, 2016*

**math**

I suspect a typo. The line from (2,0) to (2,8) is vertical. So, all the other lines must also be vertical or horizontal. They are not. and I think you meant "vertices" of a square...
*May 16, 2016*

**physics**

unless you have some idea of the mass of the galaxy, you are stuck. Once you have that, just divide by the sun's mass to see how many "suns" there are in the galaxy.
*May 16, 2016*

**Math**

just add up the changes x + 12 + 3 = 44
*May 16, 2016*

**math**

well, how many tiles will it take? multiply that by the cost of each tile.
*May 16, 2016*

**maths**

start with the sum-to-product formula: sin(√(x+h))-sin(√x) = 2cos((√(x+h)+√x))/2)sin((√(x+h)-√x)/2) or, try substituting u = √x sin(√x) = √x sin(√x) / √x = u * sin(u)/u and you know that lim sin(u)/u = 1
*May 16, 2016*

**Geometry**

the distance between those two points is √125 The equation is (x+4)^2 + (y+3)^2 = 125 You have mangled the question somehow. None of the equations has the correct center or radius.
*May 16, 2016*

**maths**

Try that again so it makes sense.
*May 16, 2016*

**Mech. Engr./Dynamics/Physics/Math**

well, you can start with the observation that the horizontal velocity is constant at v0 * sinθ Now just figure the time needed for each hop, and see if the ball travels enough to skip a step or hit it twice. Of course, you will need to have data on the height and width of...
*May 16, 2016*

**mathematics**

if they are the sides of a hexagon, the just add them up.
*May 16, 2016*

**Math**

all correct
*May 16, 2016*

**math**

7.5" = 10' 10.5" = 14' 10x14 = 140 ft^2
*May 16, 2016*

**Math**

review your basic trig functions. Draw a diagram, and you can easily see that cosθ = 1.5/6
*May 16, 2016*

**Pre-Calc College**

the fraction left after t minutes is (1/2)^(t/29) so, after two hours (120 minutes), the fraction left is 1/2^(120/29) = 0.0568 To find how log it takes to get to 10mg, 650(1/2)^(t/29) = 10 (1/2)^(t/29) = 1/65 t/29 = log(1/65)/log(1/2) = 6.022 t = 174.65 or, almost 3 hours ...
*May 16, 2016*

**Maths**

100000cm = 1km so, the scale is 1cm : 1km that should help
*May 16, 2016*

**math**

the integers form an arithmetic sequence, with a = 1 d = 1 So, the sum of the 1st 1000 integers is 1000/2 (2+999) = 500500 This is just an illustration of what Gauss figured out as a kid. You can pair up the numbers starting from the ends 1+1000 2+999 3+998 ... 500+501 There ...
*May 16, 2016*

**math**

since they are equal, 2x = 100
*May 16, 2016*

**Trigonometry**

Draw a diagram, then take a look at the cot function and you will see that h cot21° - h cot32° = 75
*May 16, 2016*

**math**

If their digit's number means the sum of the digits, then there are lots of them. But if since a quotient is only defined for two numbers, that implies that the number is a 2-digit value. I can't think of any two digits whose quotient is 20 and whose sum is 11. I ...
*May 16, 2016*

**Math**

x = y-13 x = 3/4 y x=39 y=52
*May 16, 2016*

**Math**

4(n-1) = 12 n-1 = 3 ...
*May 16, 2016*

**maths**

If one part is 2/7 of the other, then we can divide 54 into 9 parts such that each is 6. Now we see that the two parts are 2*6 = 12 7*6 = 42 12 is 2/7 of 42
*May 15, 2016*

**Integral calculus**

As a check, the theorem of Pappus says that the volume is the area times the distance traveled by the centroid, which is 9π*6π = 54π^2.
*May 15, 2016*

**algebra/trigonometry**

the easy way is to remember that the sides of a 30-60-90 triangle are in the ratio 1:√3:2 You have a long side of 75, so the other two sides are 75/√3,75,150/√3 The string is the long side. Or, using trig, the length of the string, x, is found using 75/x = ...
*May 15, 2016*

**Math**

If we let x = weight of camera y = weight of lock z = weight of crown we have x+y=330 x+z=670 y+z=470 now just solve for x,y,z
*May 15, 2016*

**Algebra**

Usually the dependent variable is on the left side. Its valye depends on the expression on the right side. The equation tells how to calculate the result of assigning a value to x.
*May 15, 2016*

**Math**

Assuming they paid the tip on the price after discount, then each paid 97.38*0.65*1.18 -------------------- = $18.67 4
*May 15, 2016*

**mathematics**

9/9^2 = 15/x^2
*May 15, 2016*

**Maths**

m = kn/p^2 now you can find k.
*May 15, 2016*

**Algebra**

3 ∑ k^2 k = -1
*May 15, 2016*

**Geometry**

atsa right
*May 15, 2016*

**Algebra**

note that the numbers grow by 3's. So, the sequence is 3k+ something. 3*1=3, but the first term is 5, so the terms are 3k+2 The sum is thus 4 ∑ 3k+2 k=1
*May 15, 2016*

**math NEED HELP**

4^3 * 4^4 / 4^9 = 4^7/4^9 = 1/4^2 or, 4^(3+4-9)
*May 15, 2016*

**Algebra**

it is clearly C, because (7x-14) = 7(x-2) but you cannot have a denominator of zero. So, while the fraction is equal to 7 almost everywhere, the value of x=2 is excluded because then the fraction is 7(0)/0 and is undefined. The numerator can be zero whenever it wants, so x=7 ...
*May 15, 2016*

**Algebra**

well, A is true, but so is C. So, the answer is D. If you had solved the quadratic you would have found both solutions 7x+84 = -x^2+40x-6
*May 15, 2016*

**Math**

44lb * 1kg/2.2lb * 14day * 30mg/(kg-day) = 8400mg
*May 15, 2016*

**maths**

give google a try. First hit explores this topic http://mathforum.org/library/drmath/view/56394.html
*May 15, 2016*

**math**

1 and 2
*May 15, 2016*

**Pre-Calc**

Sure; it's just part of the expression. So, assuming we start with n=1, the powers and denominators go up as 3,5,7,9,... So, the sequence is -x^3/3!, x^5/5!, -x^6/7!, ... though I suspect that maybe we start at n=0. But you can fix it if that's the case.
*May 15, 2016*

**Math**

1/8 - 1/9 = 1/72 That's how much of the tank gets filled in one minute with both taps open, right? But the question is poorly worded...
*May 15, 2016*

**Math**

4x^2 + x + 9 = 0 the quadratic formula will provide you with the complex roots.
*May 15, 2016*

**Math**

use the pythagorean theorem.
*May 15, 2016*

**Math**

that is very bogus notation. Try rewriting it with ^ denoting a power, as x^2 = x squared And lose the combined fractions. Use parentheses to delineate the meaning. 2/3/4 might be (2/3)/4 or 2/(3/4) which are not the same.
*May 15, 2016*

**Algebra**

C is wrong. Check your +- signs during the expansion
*May 15, 2016*

**Maths**

smallest answer will come from subtracting the largest value from the smallest. So, 0 - 7654321
*May 15, 2016*

**Prealgebra**

no idea what two-ni means, but the product of 1 2/5 and b is 1 less than 2 1/2 of b can be written as (1 2/5)b = (2 1/2)b - 1 maybe you can take it from there...
*May 15, 2016*

**calculus question ?**

You are correct in both cases. Consider f(x) = 1/x and f(x) = tan(x)
*May 14, 2016*

**math**

since xy=k, a constant, you need y such that 4y = 8*24
*May 14, 2016*

**Maths**

surely you have the formulas necessary. Just plug in your numbers.
*May 14, 2016*

**Geometry**

looks good
*May 14, 2016*

**Math**

Huh??? The only one of those answers less than 4 hours is A!
*May 14, 2016*

**Math help.**

well, plug in -x+13 for y and you get -x+13 = x^2+6x+7 x^2+7x-6 = 0 This has two solutions, but they are not listed among the choices. Check for a typo.
*May 14, 2016*

**Algebra**

t^6 + t^3 - 8 = 0 now just use the quadratic formula for t^3: t^3 = (-1±√33)/2 Now you can use de Moivre's formula to get the various cube roots of those two values.
*May 14, 2016*

**Physics**

F = ma, so a = 4 m/s^2 v = at, so 8 = 4t. t=2 s s = 1/2 at^2 = 2*4 = 8 m
*May 14, 2016*

**math**

check for a typo. There are two solutions, but they are not listed.
*May 14, 2016*

**Math**

just do them step by step -x(5x-4) (-x)(5x) + (-x)(-4) ... 5k^2(-6k^2-2k+6) (5k^2)(-6k^2) + (5k^2)(-2k) + (5k^2)(6)
*May 14, 2016*

**Algebra**

to have one root, the discriminant must be zero. That is, 4+16m = 0
*May 14, 2016*

**math (PLZ HELP ASAP)**

p = 2d p+2 = 3(a+2) d = a+5 p+2 = 3(d-5+2) = 3(p/2 - 3) p+2 = 3/2 p - 9 p/2 = 11 p = 22
*May 14, 2016*

**Math**

same as the previous question. Just plug in the values and evaluate.
*May 14, 2016*

**Math**

just plug in their values: f(x)-g(x) = (3x+5) - (-x+9) now just simplify
*May 14, 2016*

**Math calculation**

how many oz per liter? multiply that by 2.5 divide that by 2.
*May 14, 2016*

**math (pLZ HELP ASAP)**

substitute t+7 for u and you get 10t + t+7 + 26 = 5(t + t+7) 11t + 33 = 10t + 35 t = 2 so, u=9 and the number is 29 check: 29+26 = 55 = 5(2+9)
*May 14, 2016*

**math (pLZ HELP ASAP)**

u = t+7 10t+u + 26 = 5(t+u) now just crank it out.
*May 14, 2016*

**Maths**

depends on the length of the wiper blade - inner and out radius. Then a = 1/2 r^2 θ
*May 14, 2016*

**maths**

greater than 96 odd with units less than tens. 97 121 71471928373 or many many others I think you have left out some information
*May 14, 2016*

**ALGEBRA**

well, 2+6 = 8, so ...
*May 14, 2016*

**geometry**

google is your friend. Try here: https://www.math.washington.edu/~king/coursedir/m444a00/syl/class/trapezoids/Trapezoids.html
*May 14, 2016*

**Maths**

.30a + .10o = .15(a+o) .15a = .05o 3a = o so as long as there are 3 times as many oranges as apples, this will work out. check: apples: 6 of 20 oranges: 6 of 60 total: 12 of 80 = 15% 30 of 100 30 of 300 60 of 400 = 15%
*May 14, 2016*

**maths**

the same (alternate interior angles)
*May 14, 2016*

**Algebra Quadratic**

you want the solution to mx-2 = x^2 to have a zero discriminant. So, since x^2 - mx + 2 = 0 has discriminant of m^2 - 8 I guess that tells you what m is, right? Take a look at http://www.wolframalpha.com/input/?i=plot+y%3Dx^2,+y%3D%E2%88%9A8+x-2,+y%3D-%E2%88%9A8+x-2
*May 14, 2016*

**math**

actually, its speed is the same. The velocity has opposite direction.
*May 14, 2016*

**math**

same as when it left. momentum is conserved.
*May 14, 2016*

**Math**

consider Mike and Fred as one person. At the table for 7, then there are 2*11P6 ways to seat them, since the 7th seat is always taken. and 5! ways to seat the others. If they do not sit at the big table, then there are 7! ways to seat that table and 2*4! ways to seat the other...
*May 13, 2016*

**Algebra**

(x+y)/2 > 0 x+y > 0 y > -x so, y can be positive or negative, depending on x. for example x = 3 y = -2 (x+y)/2 = 1/2
*May 13, 2016*

**PLZ HELP ASAP math**

p = 2d p+2 = 3(a+2) d = a+5 Now just crank it out.
*May 13, 2016*

**Math**

A The last digit must be 0 or 5, and the 1st digit is not 0, so ending in 0: 5*4*1 ending in 5: 4*4*1 B toss out all those starting with 8 or 9.
*May 13, 2016*

**Geometry**

the middle is the average of the two ends.
*May 13, 2016*

**Geometry**

you've posted a lot of these, and all you have to do is use your formulas. We can check your answers.
*May 13, 2016*

**Geometry**

clearly the base sides and the altitude will be 18, so v = 1/3 * 18^3
*May 13, 2016*