Friday

February 12, 2016
Total # Posts: 37,586

**Math**

#1. Nope. Add 7 to both sides #2. Nope. What is 5.5-4.5 again? #3. Nope. Subtract 12 from both sides #4. Nope. At least means not less than, right? Batting a big zero on this one.
*January 12, 2016*

**Algebra**

if the width is w, then the length is 200-w. (why?) the area is w(200-w). Can you take it from there?
*January 12, 2016*

**Math**

75 * 1.20 = 90
*January 12, 2016*

**Calculus**

800 @ 140° = <514,-613> 130 @ 27° = <59,116> So, you want <x,y> such that <x,y>+<59,116> = <514,-613> Once you have x and y, then convert back to speed and heading.
*January 12, 2016*

**maths**

it will float if its density is less than water's (1g/cm^3) so, figure your density and then answer the question.
*January 12, 2016*

**Math**

3x/3 = x so, ...
*January 12, 2016*

**math**

Since constants cannot intersect lines or parabolas in infinitely many points, and lines cannot intersect parabolas in more than two points, D is the only choice: the two expressions describe the same parabola.
*January 12, 2016*

**Geometry 1 question**

just use your distance formula. Or, the Pythagorean Theorem. Plot the points. The distance you want is just the hypotenuse of a right triangle with legs 8 and 3. So, it is √(8^2+3^2) Better study your material some more.
*January 12, 2016*

**MATH help**

B is exactly the opposite of true. The output depends on the input. Try C. Usually when making a table, you list the values of the independent variable, and then figure out the dependent values in column 2.
*January 12, 2016*

**Algebra help help!!!**

4^x-3^(x-1/2)=3^(x+1/2)-2^(2x-1) 4^x - 3^x/√3 = √3 3^x - 4^x/2 (3/2) 4^x = (√3+1/√3)3^x (3/2) 4^x = (4/√3) 3^x (4/3)^x = (8/√27) (4/3)^x = (4/3)^(3/2) x = 3/2
*January 12, 2016*

**PHYSICS**

there is no atom just free electrons which disperse or are attracted by some other charged particles
*January 12, 2016*

**Physics Component Method**

the components are (just as in polar coordinates): x = r cosθ y = r sinθ You have r and θ, so plug and chug.
*January 12, 2016*

**Shurley English**

true, but the words are preposition, noun, noun, conjunction, pronoun, verb, adjective, adjective, noun, preposition, noun.
*January 12, 2016*

**Algebra**

If there are x multiple-choice questions, then there are 15-x open ones. 4x + 12(15-x) = 100
*January 12, 2016*

**Calculus help!!!**

good luck with that! since e^u is always positive, you need y>0 and x>0 Since e^xy > 1, and grows very fast, I seriously doubt that x^2y will ever catch up, and sinxy is insignificant. Let y=0 or x=0 x^2y+sinxy=0 but e^xy=1 You can see that the slope of x^2y+sinxy is ...
*January 12, 2016*

**math**

b/g = 2/5, so 5b=2g g = b+9 Now just solve for b and g.
*January 12, 2016*

**Trigonometry - wow!**

Good luck with that! I have no clue how to get an exact solution. The graphs at wolframalpha.com and the analysis provided there don't give me much hope: http://www.wolframalpha.com/input/?i=2tanx+cos2x%2B1%3Dtan3x%2B2cos2x
*January 12, 2016*

**Homework for Math**

park area: 60*100 = 6000 If the terrace has uniform width w, then garden area is (60-2w)(100-2w) (60-2w)(100-2w) = 3000 Now just solve for w.
*January 12, 2016*

**Maths**

LCM(5,6,8) = 120 So, every 120 seconds they all fire together.
*January 12, 2016*

**Calculus**

Let x be the number of price decreases. Then the revenue is r(x) = (900-100x)(5000+1500x) = 100*500(9-x)(10+3x) = 50000(-3x^2+17x+90) Now find when dr/dx=0 and you can figure the price for maximum revenue.
*January 12, 2016*

**Calculus**

I'd say the critical point exists, since the usual definition that y'=0 or is undefined. In either case, I think that (3,0) is the critical point.
*January 12, 2016*

**calculus**

d/dx f^2 = 2f df/dx ∫ lnx/x dx Since we are discussing f^2, let's let f(x) = (lnx)^2 df/dx = 2 lnx * 1/x = 2lnx/x So, clearly, ∫lnx/x dx = (lnx)^2/2 + C check, using integration by parts: u = lnx dv = dx/x du = 1/x dx v = lnx ∫lnx/x dx = lnx*lnx - ∫...
*January 11, 2016*

**Calculus**

well, from the graph at http://www.wolframalpha.com/input/?i=+2+cos%28x%29+%2B+%28cos%28x%29%29^2 I'd say you were wrong. f = 2cosx + cos^2(x) f' = -2sinx - 2sinx cosx = -2sinx(1+cosx) f'=0 where sinx=0 or cosx = -1 x = 0 or pi
*January 11, 2016*

**Calculus**

1/2 ∫ 1/(sin(x/2)cos(x/2))dx let u = sin(x/2) du = 1/2 cos(x/2) dx or, dx = 2/cos(x/2) du Then you have 1/4 ∫1/u 2/(cos(x/2))dx = 1/4 ∫ 1/u du = 1/4 ln(sin(x/2)) + C Now, we all know that ∫ csc(x)dx = -ln(cscx + cotx) so what gives here? 1/4 ln(sin(x/2...
*January 11, 2016*

**Mathematics**

If there were x correct answers, then there were (120-x) incorrect answers. So, x - (120-x)/4 = 80
*January 11, 2016*

**math**

clearly the radius of the circle is 3. So, what is pi * 3^2 ?
*January 11, 2016*

**Math**

you know that tan(x) -> ∞ as x -> π/2 so, what do you think?
*January 11, 2016*

**math 1**

4":14' = 4":(14*12)" = 1:42
*January 11, 2016*

**math 1**

error was 10 10/85 = ?
*January 11, 2016*

**Math**

not differentiable if f'(x) is undefined. f'(x) = 1/√(1-x^2) so f' is undefined at x=±1 Now review the principal values of arcsin(x) cusps and corners are not differentiable, since the limit of f' is not the same from both sides.
*January 11, 2016*

**math**

since each triangle has sides 1/2 as big, the areas are 1/4 as big. So, just form a G.P. of the desired quantities and work with that.
*January 11, 2016*

**Math**

a+c = 9 8a+5c = 54
*January 11, 2016*

**Math**

Assuming you mean (5m^6)/(3n) that is just 5/3 m^6/n If the n is a typo, then you have 5/3 m^5
*January 11, 2016*

**math - eh?**

no idea what you're asking. Care to elaborate a bit?
*January 11, 2016*

**Math**

if you want 12, buy 10. If you want 26, buy 20 and that gives you 24, so then 2 more.
*January 11, 2016*

**MATHS**

just use the power rule and integrate each term separately. recall that ∫x^n dx = 1/(n+1) x^(n+1)
*January 11, 2016*

**math**

4n-3 <= 21
*January 11, 2016*

**Math (Help) thx!**

negative exponents move values from numerator to denominator and vice-versa. 7^-2 = 1/7^2 = 1/49
*January 11, 2016*

**Math**

(n+4)+n(n+2)+n=0 (n+4)+n(n+2+1)=0 (n+4)+n(n+3) = 0 n+4+n^2+3n = 0 n^2+4n+4 = 0 (n+2)^2 = 0 n = -2 or, n+2+2 + n(n+2) + n = 0 (n+2)+n(n+2) + n+2 = 0 2(n+2)+n(n+2) = 0 (n+2)(n+2) = 0 (n+2)^2 = 0
*January 11, 2016*

**Math log equation**

5^2x = (5^x)^2 So, make things easier to look at by letting u = 5^x Then you have u^2+20u-125 = 0 (u+25)(u-5) = 0 u = -25 or 5 But, 5^x is never negative, so we end up with u=5 5^x = 5 x = 1 check: 5^2 + 20*5 -125 = 25+100-125 = 0
*January 11, 2016*

**Math**

selling price will be 450000*1.03^10 Then just subtract the initial cost to get the profit.
*January 11, 2016*

**Math**

6 - (-2) C'mon, read your text.
*January 11, 2016*

**Math**

since the slope is constant, you need (n-4)/(6+2) = (4-1)/(-2-1) Now you can find n. Or, thinking about it another way, y increased by 3 when x decreased by 3. So, y will decrease by 8 if x increases by 8.
*January 11, 2016*

**Math log help**

Geez - give it a break, willya? Check your previous posts and be willing to wait a bit...
*January 11, 2016*

**Math**

Been there, done that http://www.jiskha.com/display.cgi?id=1452547715
*January 11, 2016*

**Math**

Not very patient, are ya? http://www.jiskha.com/display.cgi?id=1452547612
*January 11, 2016*

**Math logs**

Assuming the usual sloppiness with parentheses, we have 10^(3x-8) = 2^(5-x) (3x-8)log10 = (5-x)log2 (3log10)x - 8log10 = 5log2 - (log2)x x(log1000+log2) = 5log2+8log10 xlog2000 = log(32*10^8) x = log(32*10^8)/log(2000) x ≈ 2.88 Or, working a different way, 10^(3x-8) = 2...
*January 11, 2016*

**Algebra logs please help**

since 9 = 3^2, log3(n) = 2log9(n) That is, the power of 3 needed for a number is twice as big as the power of 9. So, we have 2log9(x) = log9(6x) log9(x^2) = log9(6x) x^2 = 6x x = 0 or 6 0 not allowed, so x=6
*January 11, 2016*

**Math**

#1 a 4x4 grid has 16 blocks Care to change your answer? #2 32% = 32/100 = 8/25 Care to change your answer? #3 6/24 = 1/4 Care to change your answer? #4 .09 = 9/100 Care to change your answer? #5 ok #6 4/9 = 0.44444... 11/25 = 44/100 That should clear things up #7 ok #8 9/15 = ...
*January 11, 2016*

**Math @angie**

your answer was easy to come by, but it did not answer the question. Also, 2/3 + 1/2 is NOT 3/5 Better review your fractions some before answering questions on them.
*January 11, 2016*

**Math**

correct. good job.
*January 11, 2016*

**Math**

did you actually try x=-6 to see whether you get the same y for both equations?
*January 11, 2016*

**Math**

well, if x=20, then y=70, since they add to 90. does 20 = 2*70-30? what did you do first?
*January 11, 2016*

**algebra**

15.99x <= 59.95
*January 11, 2016*

**@Studier2004**

42/6 is indeed 7, but it is not the answer to the question.
*January 11, 2016*

**math**

If the length is L, then 2(w+L) = 42 2(6+L) = 42 ...
*January 11, 2016*

**Math**

correct on all three.
*January 11, 2016*

**MATH HELP**

don't see any gold stars. You want to just write the question number, followed by your answers?
*January 11, 2016*

**Math**

correct.
*January 11, 2016*

**Math**

Hmmm. does 34 = 32?
*January 11, 2016*

**Math**

multiply the top one by 2, and you have 3x+4y=22 3x+6y=22 Now what do you think?
*January 11, 2016*

**Math**

whatever you do to one side, you must also do to the other side, if they are to remain equal. You subtracted x in your first step, but only on the left. If you had tried a value for x and y, you would have seen that your solution was wrong. y = -x+7, so let x=1, and y is -6. ...
*January 11, 2016*

**algebra 1**

multiply the 2nd equation by 5 and you have 3x-5y = 21 10x+5y = 5 Now you can eliminate y and get x, then figure y.
*January 11, 2016*

**Math**

The water level rose 2 cm. So, the volume of the stones is 2*20*15=600 cm^3 This assumes that the stones were completely covered by water.
*January 11, 2016*

**Math- steve? reiny?**

Does f^-1(x) even exist? f'(x) = 5x^4+6x^2+1 That is always positive, which means that the graph of f(x) does not change direction, so it passes the horizontal-line test. where is f(x) = 3? x^5+2x^3+x-1 = 3 x^5+2x^3+x-4 = 0 a little synthetic division shows that x=1 is a ...
*January 11, 2016*

**Math**

divide into 5 equal parts. Then use 1 part and 4 parts for the lengths.
*January 11, 2016*

**Algebra**

s = 3d m+1 = 6d m+10 = 14+(s+10)+(d+10) solve to find m. I get non-integer values for s and d. If "three times older" means d+3d=4d, then I get integer values, but the man is 149. Not likely.
*January 10, 2016*

**Algebra (Quadratic)**

If the width is w, the length must be 50-w. So, the area is a = w(50-w) The maximum area is achieved when x=25. You can find what it is. Note that the max area is when the rectangle is a square.
*January 10, 2016*

**maths**

If you mean 6x^2-x+3 < 5x^2+5x-5 then just collect terms on one side, and you get x^2-6x+8 < 0 (x-2)(x-4) < 0 This is a parabola which opens upward, so it is negative between the roots. Thus 2 < x < 4 A product is negative if exactly one of the factors is negative.
*January 10, 2016*

**Mathematics**

If you are using A for θ, then clearly θ=π/4 is a straight line with slope 1, so that is just y = x r = a sin2θ r = 2a sinθ cosθ r^3 = 2a rsinθ rcosθ (x^2+y^2)^(3/2) = axy But that only gives half of the graph, where xy is positive.
*January 10, 2016*

**Calculus**

surely you jest! The critical points are where f' = 0. f'(x) = -3sin3x You know that sin(u)=0 when u is a multiple of pi. So, f'(x) = 0 when 3x is a multiple of pi: x= 0, pi/3, 2pi/3, ...
*January 10, 2016*

**Trig - 9th grade**

this doesn't look easy. I'd attack it like this: 10sinx cosx + 3sinx - 1 = 0 sinx(10cosx+3) = 1 sinx = 1/(10cosx+3) sin^2x = 1/(100cos^2x + 60cosx + 9) (1-cos^2x)(100cos^2x+60cosx+9) - 1 = 0 Expand that out, and you have a 4th-degree polynomial in cosx. Guaranteed not ...
*January 10, 2016*

**maths**

we see that both pipes together can fill the the tank in 120/7 minutes: 1/t = 1/40 + 1/30 t = 7/120 So, after 5 minutes, they have filled 35/120 = 7/24 of the tank. So, it will take A 7/24*40 = 35/3 minutes to fill the rest. Total time: 5 + 35/3 = 16 2/3 minutes.
*January 10, 2016*

**Calculus**

while f" = 1/x, f is not defined for x<=0. So, f is concave up for all x>0. f = 2^(x/2) f' = ln2/2 2^(x/2) f" = (ln2/2)^2 2^(x/2) This is just e^kx in disguise. It is concave up everywhere. There are no critical points. f' = x√(9-x^2) f'=0 at ...
*January 10, 2016*

**Math**

If the calorie content of the pies are p and h, respectively, then we have (1/2)p + (3/4)h = 765 (1/4)p + h = 745 Now just solve for p and h. It might be less cumbersome to clear the fractions: 2p + 3h = 3060 p + 4h = 2980
*January 10, 2016*

**Algebra**

OHH! Thank you very much, that would have been a pretty frustrating error if I continued without noticing! Thank you, Damon. Have a great night!
*January 9, 2016*

**Algebra**

so it would then turn into 9y+12y+15y-45=243 36y-45=243 ( add the y's together) 36y = 288 (add 45 to 243) y = 8? (288 divided by 36)
*January 9, 2016*

**Algebra**

If someone could just show me how to set up a formula that would be great!
*January 9, 2016*

**Algebra**

A stamp collection consists of 3¢, 12¢, and 15¢ stamps. The number of 3¢ stamps is three times the number of 12¢ stamps. The number of 15¢ stamps is three less than the number of 12¢ stamps. The total value of the stamps in the collection is...
*January 9, 2016*

**Geometry**

hard to say, without knowing T,U,V
*January 9, 2016*

**MATH Precalculus**

Draw a diagram! clearly, if f(t) is the distance in feet, for 0<=t<=6, f(t) = 15t for 6<=t<=12, f(t) = √(90^2+(15t)^2)
*January 9, 2016*

**geometry**

s = rθ = r(2π/12) = π/6 r
*January 9, 2016*

**math**

You know from eq #2 that y=x+4. So, plug that into eq #1 and you have x + 4(x+4) = 1 Now you can find x.
*January 9, 2016*

**Math**

the surface area is 2πr^2 + 2πrh = 2π(r^2+hr) Now it's clear that r^2+hr=16... Now, using h=r+4, you have 2πr(r+r+4) = 32π
*January 9, 2016*

**physics**

the circumference is 4π. SO, the angular velocity is 16m/s * 1rev/4πm * 2πrad/rev = 32π/4π = 8 rad/s
*January 9, 2016*

**Direct variation algebra 2**

since V = kG, V/G=k, a constant. So, you want to find V such that V/11 = 36/4
*January 9, 2016*

**math**

What GP's are possible? If the 3 numbers are chosen independently, then we have 1,1,1 1,2,4 1,3,9 1,4,16 1,5,25 1,6,36 1,7,49 2,2,2 2,4,8 2,6,18 2,8,32 2,10,50 3,3,3 3,6,12 3,9,27 3,12,48 4,4,4 4,8,16 4,12,36 5,5,5 5,10,20 5,15,45 6,6,6 6,12,24 and so on. If the three ...
*January 9, 2016*

**math**

area of a circle is pi r^2 So, how far could the bear have walked in 4 hours? 4*2=8. use that for the radius. Then use 5*2 for the radius in the 2nd part, then subtract.
*January 8, 2016*

**Calculus @ Henry**

I worked some on this earlier, and botched it a bit, so here goes again. A water tank is made by rotating f(x)=2^x-1 between [0,2] about the y-axis. The water tank is initially full, when a hole is opened at the bottom tip so that the water drains at a rate of 4 unit^3/second...
*January 8, 2016*

**Geometry**

The first problem is discussed here: http://www.algebra.com/algebra/homework/Triangles/The-line-segment-joining-the-midpoints-of-two-sides-of-a-triangle.lesson Google is your friend. Most problems posted here have been discussed many times on the web. For #2, if you draw a ...
*January 8, 2016*

**Algebra**

The sum of two numbers is fourteen. Using x to represent the larger of the two numbers, translate "the difference between five more than the larger number and three times the smaller number" into a variable expression. Then simplify.
*January 8, 2016*

**Calculus**

hint: since a = s^2, da = 2s ds
*January 8, 2016*

**apex geometry**

too many typos to proceed. No diagram, but then none needed, since all circles are similar.
*January 8, 2016*

**maths**

x+19 = 48 x = 48-19 ...
*January 8, 2016*

**calculus**

If the radius of the circle is x, the side of the triangle is y, and the side of the square is z, then we have 2πx+3y+4z = 1 a = πx^2 + √3/4 y^2 + z^2 da/dx = 2πx da/dy = √3/2 y = √3/2 (1-2πx-4z) da/dz = 2z a will have a maximum where all ...
*January 8, 2016*

**maths**

At any point (x, 3/2 x) on the line, the distance from the origin is d^2 = x^2 + 9/4 x^2 = 13/4 x^2 If the circle's center is at (h,3h/2), then, we have (x-h)^2 + (y-(3h/2))^2 = 13/4 h^2 (5/2-h)^2 + (1/2-(3h/2))^2 = 13/4 h^2 h=1 So, the circle is (x-1)^2 + (y-3/2)^2 = 13/4...
*January 8, 2016*

**calc**

what's with all the words? s(t) = -t^3/3 + 13t^2/2 - 30t when the particle is mofing to the right, s(t) is increasing, so ds/dt > 0 -t^2 + 13t - 30 > 0 3 < t < 10 Since our domain is 0<t<9, our interval is thus 3<t<9
*January 8, 2016*

**maths**

2s^2 = 98 s = 7
*January 8, 2016*

**Calculus**

When the height of the water is y, then the radius of the surface is x=log_2(y+1) Thus, the volume of the water when the depth is h is ∫[0,h] πx^2 dy Now, ∫π(log_2(y+1))^2 dy = π(y+1)(ln^2(y+1)-2ln(y+1)+2)/ln^2(2) That gives me ∫[0,3]π(...
*January 8, 2016*

**Geometry**

since consecutive angles add to 180, we have 8x+1 + 12x+19 = 180 Now find x, and then the angle measure.
*January 7, 2016*