Friday

August 22, 2014

August 22, 2014

Total # Posts: 24,371

**geometry**

The slope of a line does not change. The length expands by the dilation factor.
*May 29, 2014*

**algebra**

so, how many watts per decibel? Divide that into 2.42*10^-5 what's this "cross"? Can't you say "times", or use the multiplication symbol?
*May 29, 2014*

**math**

(1) The sides are x and y, so y = 400-x The area is thus a = xy = x(400-x) (2) If the side x is parallel to the water, x+2y = 400, so y = (400-x)/2 and the area is a = xy = x*(400-x)/2 (3) x+y=200, so the area is a = xy = x(200-x) If you need to find the maximum area, just ...
*May 29, 2014*

**algebra**

3 = x-3 6 = x As for the other, I can't quite decode your weird text. I can say that ln e = 1 ln √n = 1/2 ln n ln a - ln b = ln(a/b) If you have ln e = ln √6 - 3ln x 1 = ln√6 - ln x^3 1 = ln √(6/x^6) e = √(6/x^6) 6/x^6 = e^2 x^6 = 6/e^2 x = (6...
*May 29, 2014*

**Precalculus**

y=2*pi*x*(25-x)^2
*May 29, 2014*

**college algebra**

If the numbers are x-1,x,x+1, then 3x = 651 x = 217 So, the numbers are 216,217,218 Don't know what was all that stuff with factors of 651. Looks like you need to study what "sum" and "consecutive" mean. The two paychecks are p and .75p. So, p + .75p = ...
*May 29, 2014*

**Algebra**

Reference angles are always measured from the x-axis. So, since 3pi/4 = pi - pi/4, the reference angle is pi/4. Better go back and review that topic some.
*May 29, 2014*

**college algebra**

you are mixing up all kinds of unrelated numbers, and then throwing darts at the calculations. If x is the slower rate, then 3x is the faster rate. So far so good. Now consider that distance = time * speed, and the total distance covered is 64 miles. Since the time for both ...
*May 29, 2014*

**MATH**

a rational number can be written as a fraction. Any terminating or repeating decimal is also rational. √5 is not rational. There is no fraction which is exactly equal to √5. The decimal value goes on forever and never repeats. It is easy to prove that √5 is ...
*May 29, 2014*

**Math - incomplete**

don't you see that there's something missing here?
*May 29, 2014*

**Algebra 2**

OK. You do understand that if the sides of the rectangle are x and y, then the area is a = xy right? Given the equation of a parabola, can you find the vertex? If y = ax^2+bx+c, then the vertex is at x = -b/2a So, in each case, figure out what x and y are, express the area a ...
*May 29, 2014*

**Algebra 2**

(1) The sides are x and y, so y = 400-x The area is thus a = xy = x(400-x) (2) If the side x is parallel to the water, x+2y = 400, so y = (400-x)/2 and the area is a = xy = x*(400-x)/2 (3) x+y=200, so the area is a = xy = x(200-x) If you need to find the maximum area, just ...
*May 29, 2014*

**Geometry**

the car moves as far as 10 times the circumference of the wheel. C = pi*d, so C = 22pi = 69.11 inches so, the car moves 691.1 inches, or 57.6 ft
*May 29, 2014*

**Algebra**

correct
*May 29, 2014*

**Math**

v = 15000 * .7^t
*May 29, 2014*

**Algebra, math**

If the plane's speed is p and the wind's speed is w, then 1200/(p+w) = 3 1200/(p-w) = 4 rearrange to get 3p+3w = 1200 4p-4w = 1200 or, p+w = 400 p-w = 300 Now just solve for p and w.
*May 29, 2014*

**How many terms are in the following polynomial?**

the powers don't really matter. The terms are separated by the + and - signs. So, just count them and add 1.
*May 29, 2014*

**Math**

You are correct in counting 2 coefficients. But, they are both positive, so (b) is correct.
*May 29, 2014*

**College Algebra**

better to use time = distance/speed, since we are adding up times here. d/35 + 15 + d/50 = 41 17/350 d = 26 d = 26 * 350/17 d = 9100/17 = 535.29 check: 535.29/35 = 15.294 535.29/50 = 10.706 total driving time is 26 hours, as expected.
*May 29, 2014*

**MATH PLZ HELP**

NO. The answer is 10/14 since there are 10 not-pink erasers out of 14 total.
*May 29, 2014*

**MATH PLZ HELP**

how many of the erasers are not pink? How many total erasers are there? P(~pink) = #~pink/#total
*May 29, 2014*

**Math**

No reason to try to use decimals. Fractions are exact. Your addition is correct.
*May 29, 2014*

**Maths ,science**

12000(1+.065)^5
*May 29, 2014*

**Trig**

The angle is θ, where tanθ = (173-5)/50
*May 29, 2014*

**statistics**

75 is 5 std from the mean of 60, so 1 std must be 3.
*May 29, 2014*

**Test and Measures**

In that case, you need to review what the Z table means. Without that, you have no context. A Z score of zero means that the value is 0 std away from the mean. In this case, it means that the score is the same as the mean, or 65. If such a question is assigned, it can only ...
*May 29, 2014*

**Test and Measures**

what score is 0 std from the mean of 65?
*May 29, 2014*

**science**

Each mole of Pb(NO3)2 will make one mole of PbO So, how many moles of Pb(NO3)2 are in 4.0 grams? What is the mass of that many moles of PbO
*May 29, 2014*

**Geometry**

you need factors of 39 which differ by 10. I suggest 3 and 13. So, x^2-10x-39 = (x-13)(x+3)
*May 29, 2014*

**math**

initial velocity is 800 ft/s upward it does not change the equation. initial position is 0, since it was fired from the ground (height=0) It falls back to the ground when h=0. So, solve for t in 800t-16t^2 = 0 Solve for t in 800-16t^2 = 6400 (why are there two solutions?) Same...
*May 29, 2014*

**geometry**

If the length is x, then 20/x = sin 75.5° Now just solve for x.
*May 29, 2014*

**math**

1/a + 1/b + 1/c = 2 If we let a <= b <= c, then there's always the easy case where a=1 b=2 c=2 I guess that's the only one, since if any of the three values is 3 or more, then the fractions can't add up to 2.
*May 29, 2014*

**Algebra**

x^2+6x+8 = 0 (x+2)(x+4) = 0 Since (x+a)(x+b) = x^2 + (a+b)x + ab you are looking for factors of 8 that add up to 6. 5w^2-3 = 0 5w^2 = 3 w^2 = 3/5 w = ±√(3/5)
*May 29, 2014*

**Math**

If she started with x dollars, 4/9 x = 20b x = 45b 10b + 5d = 5/9 x We want the ratio d/b. So, 10b + 5d = 5/9 * 45b 10b + 5d = 25b 5d = 15b d/b = 3
*May 29, 2014*

**math**

The cat runs 4/7 as fast as the dog. So, if the dog has to run x meters, the cat will have run 4/7 x during that time. x = 12 + 4/7 x 3/7 x = 12 x = 28 That is, the cat will have run 16 meters while the dog runs 28 meters, having made up the cat's 12-meter head start.
*May 29, 2014*

**Math 8th grade**

Take a look at the last terms: x and 3x-2 So, for all the other places where x is given, y = 3x-2 Where y is given, x = (y+2)/3 Now just fill in the blanks.
*May 29, 2014*

**Math**

a = -12 d = 3 S = n/2 (-12 + 39) Your mission, should you choose to accept it, is to figure out how many terms there are (n) from -12 to 39
*May 28, 2014*

**math**

If there are x ounces of the cheap tea, then the rest (32-x) is expensive. The cost of the mix must be the total of the costs of the components, so 3.99x + 8.99(32-x) = 5.99*32 Now just solve for x.
*May 28, 2014*

**algebra**

2x-x^3 >= 0 x(2-x^2) >= 0 This function crosses the x-axis at the roots, which are at x = -√2, 0, √2 Now, you know that y is negative for large negative x, so y < 0 in (-∞,-√2) y >= 0 in [-√2,0] y < 0 in (0,√2) y >= 0 in...
*May 28, 2014*

**College Algebra**

The common denominator is 2(x-2). If you multiply through by that, you get x - 7*2(x-2) = 1*2 Now just proceed normally: x - 14x + 28 = 2 -13x = -26 x = 2 For the next one, you must be interpreting the equation as 1/(2y) + 4 = 1/(7y) if you multiply by 14y, you get y + 4*14y...
*May 28, 2014*

**College Algebra**

How did it not work out? Show us what you tried and why you think it's wrong...
*May 28, 2014*

**College Algebra**

2/9 + -5/6 = -8 - (-3/7 k) 2/9 - 5/6 + 8 = 3/7 k 133/18 = 3/7 k 931/54 = k I suspect a typo. Show your steps, as I see no way to get 82k from that input.
*May 28, 2014*

**algebra**

Assuming a typo, and you meant peanuts instead of almonds, we have 2.95p + 7.95(80-p) = 6.50*80 p = 23.2 So, 23.2 lbs of peanuts and 56.8 lbs of cashews or whatever the nuts really are.
*May 28, 2014*

**Math**

If the base of the triangle is 2b, then b/h = tanθ, so b = h tanθ The area A = 1/2 (2b)(h) = bh = h^2 tanθ So, θ = arctan(A/h^2)
*May 28, 2014*

**geometry**

All I see is a then-clause. No conditions appear to be involved. But, I suppose you could say If: the product of x and y is an odd multiple of 5 AND: x and y are integers Then: x or y is a multiple of 5 AND x and y are odd Without those AND conditions, not much can be said ...
*May 28, 2014*

**algebra**

If you plot both values on the number line, you will see that -2/3 is to the right of -1, so the statement is false.
*May 28, 2014*

**Math Algebra**

Assuming you mean 2/(3x) + 4/x = 7/(x+1) then multiply through by (3x)(x+1) and you have (with x≠0 or -1) 2(x+1) + 4*3(x+1) = 7(3x) 2x+2 + 12x+12 = 21x 7x = 14 x = 2
*May 28, 2014*

**decimals**

The number is a.bcd the digit in the hundreths place of 4.361 is 6, so, c>6 the digit in the tenths place of 2.85 is 8, so d>8 a.b = 8.6 So, we have 8.6[789]9 where the 3rd digit can be any of those in brackets.
*May 28, 2014*

**Math**

1. No - surely you have drawn pgrams which are not squares. 2. No - but 3. Yes 4. Yes 5. No - a rhombus has all sides equal Looks like you need to review your definitions some, and play around drawing some figures, with sides of various lengths and slants.
*May 28, 2014*

**Mathamatics**

you don't solve an identity -- you prove it. 1-cos^2θ = sinθ cosθ/cotθ since cotθ = cosθ/sinθ, now we have sin^2θ = sinθ sinθ QED (1-cos^2θ)(1-tan^2θ) = (sin^2θ-2sin^4θ/(1-sin^2θ) sin^2θ(1-tan^...
*May 28, 2014*

**Harris**

that would be 2(3x + 5 + x +7) = 8x+24
*May 28, 2014*

**Math**

these are all standard angles you should know by heart. It will save you a lot of trouble working them out all the time. -1 - 1 + 1 - 2 + 2 + 1 = 0 It also involves knowing the signs of the trig functions in the various quadrants, and how to figure the reference angle. Also, ...
*May 28, 2014*

**Math**

5{3a-2b(3a+6b)+6a} 15a-10b(3a+6b)+30a 15a-30ab-60b^2+30a 45a-30ab-60b^2
*May 28, 2014*

**Geometry**

I'm sure the question is correct. You probably want to know whether your answer is correct. I believe you are right in your choice.
*May 28, 2014*

**Math**

If you want to use vector notation, then if the vector to A is a, and to B is b, etc. Then AB = b-a BC = c-b CA = a-c AB+BC+CA = b-a+c-b+a-c = 0 AB is b-a because if there is a vector u such that a+u=b, then u=b-a.
*May 28, 2014*

**Math**

Looks to me like AB + BC + CA = 0 Similarly for the other one. Getting back to A, the sum is just 0 again. The vectors form a closed polygon, so the net result is zero.
*May 28, 2014*

**math**

54-24 = ?
*May 28, 2014*

**math**

30 <= 18+0.3(x-50) <= 45 12 <= .3(x-50) <= 27 40 <= x-50 <= 90 90 <= x <= 140
*May 28, 2014*

**algebra**

what's with the braces? Just use vertical bars: |8| = 8 |-9| = 9 and so on |x| = -x if x is negative otherwise, |x| = x
*May 28, 2014*

**geometry**

the scale Q'/Q = 2/3 2/3 * 15 = 10, the new length
*May 28, 2014*

**Geometry**

consecutive angles are supplementary opposite angles are equal So, what do you have here?
*May 28, 2014*

**geometry**

my first guess is you are allergic to that fruit.
*May 28, 2014*

**geometry**

2 - 3 = -1 Oops. If by difference, you mean the larger minus the smaller, the conclusion is true. Technically, though, the difference is minuend - subtrahend ----------------- difference So it matters which is which.
*May 28, 2014*

**math**

MS Sue is trying to get you to figure out 8*(6ft+4in) = 8*6ft + 8*4in = 8*6*12in + 4in = ? in
*May 28, 2014*

**7th grade math**

(2/5 x) > 7 x > 7 * 5/2 x > 35/2 So, place a dot at 35/2 and shade to the right 2(x+7)-4 > 5(x-3) 2x+14-4 > 5x-15 2x+10 > 5x-15 25 > 3x 25/3 > x So, place an open circle at 25/3 and shade to the left
*May 27, 2014*

**Calculus**

This is indeed the MVT. The secant line through (1,1/3) and (4,2/3) has slope 1/9. The MVT says that in the interval (1,4), there is some c where f'(c) = 1/9. f'(x) = 2/(x+2)^2 So, we want c such that 2/(c+2)^2 = 1/9 (c+2)^2 = 18 c+2 = ±3√2 c = -2±3...
*May 27, 2014*

**Calculus**

use integration by parts u = x, du = dx dv = cos 15x dx, v = 1/15 sin 15x Now we have ∫x cos15x dx = 1/15 x sin15x - ∫1/15 sin15x dx And that's clear sailing. . . right?
*May 27, 2014*

**algebra/geometry**

no idea. However, what you have factors into (x-7)(x+4) = 0 Then the roots are clearly 7 and -4
*May 27, 2014*

**IB Maths SL**

The slope of the tangent to f(x) is f'(x) = (g'h-gh')/h^2 So, the normal has slope h^2/(gh'-g'h) At x=2, that is 6^2/(18*2-5*6) = 6 f(2) = g(2)/h(2) = 18/6 = 3 So, now you have a point and a slope, so the normal line at x=2 is y-3 = 6(x-2)
*May 27, 2014*

**Cosine Law NEED HELP QUCIK**

at 9:30 the hour hand has gone clockwise 9.5/12 * 360 = 285° from the top The minute hand is at 180° So, the angle between them is 105°. You want d where d^2 = 12^2 + 10^2 - 2*12*10*cos 105° d^2 = 306.1 d = 17.5 Just a straightforward application of the law of ...
*May 27, 2014*

**Geometry**

Just looking at the figure, angles AHM and TMH are congruent, so 3x+5 = 7x-27 x = 8 So, m<AHM = 29 If you answered #15, #17 should have been obvious.
*May 27, 2014*

**Calculus**

v = ∫[1,t] πr^2 dx where r=y=1/x. So, v = π∫[1,t] 1/x^2 dx = π(-1/x) [1,t] = π(1 - 1/t) as t→∞, v→π
*May 27, 2014*

**Algebra 1--Please, help me! (Steve)**

by now these should be getting easier. When multiplying/dividing powers, add/subtract the exponents. 3r^2t/6st^3 x 2r^2s^3t^2/8r^4s^2 = (3*2)/(6*8) r^(2+2-4) s^(-1+3-2) t^(-3+1+2) = 1/8 You gotta start using parentheses... x^2 + x/x^2 + 3x + 2 + 3/x + 2 = (x^2+x)/(x^2+3x+2) + ...
*May 27, 2014*

**physics-force and pressure**

well, geez - pressure is force/area, so that would be 300N/700cm^2 = 3/7 N/cm^2 Chances are you should convert that to N/m^2 so your answer could just be in Pa.
*May 27, 2014*

**Algebra 1**

you are correct
*May 27, 2014*

**Algebra 1**

You got (a) correct. So, for (b), just plug in x=5 and evaluate the fraction.
*May 27, 2014*

**Algebra 1**

yes, #1 = 2a^2b/c^2 #2 = 1/(3x-15)
*May 27, 2014*

**Algebra 1**

Hmmm. How about 2a^2b / c^2
*May 27, 2014*

**Algebra 1**

when dividing by a fraction, just invert and multiply. So, #1 3a^4b/2a^2c^3 * 8c^4/12a^2c = 3*8/12 a^4/a^2 b c/c^3 ... #2 x^2+4x-5 = (x+5)(x-1) x^2-25 = (x+5)(x-5) So, you just have (x+5)(x-1) / 3(x-1) * 1 / (x+5)(x-5) = (x+5)(x-1) / 3(x+5)(x-1)(x-5) = ...
*May 27, 2014*

**Algebra 1--Please, help me!**

#1 also t=0, since t^2-t = t(t-1) The original expression must be examined for excluded values. (t-1)/(t^2-t) = 1/t, so t≠0. But dividing top and bottom by t-1 to get there means that t≠1, because you cannot divide by zero. #2 huh? There is no x-2 in the ...
*May 27, 2014*

**math**

x(x-2) + y(x-2) (x+y)(x-2)
*May 27, 2014*

**trig - incomplete**

as usual, draw a diagram and recall your basic trig definitions. If the ledge is at height a, and at distance x from the tree (with height h), then we have (h-a)/x = tan25° a/x = tan10° Now eliminate a to get h-x tan25° = x tan10° h = x(tan25°+tan10°) ...
*May 27, 2014*

**algebra**

take a look at http://www.wolframalpha.com/input/?i=solve+z^5+%3D+i Note that the angles given are pi/2 + k*2pi/5
*May 27, 2014*

**Math**

if y = u^v, where u and v are functions of x, y' = v u^(v-1) u' + ln(u) u^v v' If you look carefully, you will see that y=u^n and y=a^v are just special cases, where u' or v' = 0. Anyway, just plug in u = x^2 v = sinx and you get (2x sinx)*(x^2)(sinx-1) + ...
*May 27, 2014*

**maths - still bogus**

1983 is not a leap year. After you fix that, just divide the number of years involved by 4, but watch for remainders. Then post your work, so we can see how you solved it...
*May 27, 2014*

**misc stuff**

If you're planning to attend a school where English is the language of choice, I suggest you improve your language and writing skills first.
*May 27, 2014*

**maths**

First, there was no 29th of Feb in 1983; that was not a leap year Second, you give no date to end the calculation.
*May 27, 2014*

**maths**

98-14 (also, the verb is "lose," not "loose." Unless she deliberately threw them away.)
*May 27, 2014*

**math**

I assume you know how to find the volumes of such solids. Just subtract the volume of the sphere from that of the cylinder. The leftover space holds the water: π(2x)^2*(2x) - 4/3 πx^3
*May 27, 2014*

**algebra 2 and Trigeonomerty**

(a) You have to multiply for the three draws, and allow for the changing population of blues and the total: 12/30 * 11/29 * 10/28 (b) That would be 18/30 * 17/29
*May 27, 2014*

**math - incomplete**

no table provided
*May 27, 2014*

**algebra**

just multiply each event by its probability. The sum is the expected value of income. Then subtract the costs involved: (395000)(1/40)+(125000)(1/20)-25000 Technically, we need all the probabilities to add to 1, so we should include the term for a dry well: (0)(37/40) but that...
*May 27, 2014*

**Algebra 1--How Am I Supposed to Solve This?!**

just divide the two, as you would do with any ratio: (πrl + πr^2) / (2πrh + 2πr^2) πr(l+r) / 2πr(h+r) = (l+r) / 2(h+r)
*May 27, 2014*

**Algebra 1--how am I suppose to graph this?!**

plot it the way you plot any function! Pick some values of x and calculate y. Then plot the point at (x,y). The curve will be smooth, but the only poi9nts that make sense in the real world are where x is a divisor of 75. Your graph should look like this: http://www....
*May 27, 2014*

**math**

mixed numbers are useless for calculation. Convert them to fractions and things get easy. 21/10 * 15/7 = ?
*May 26, 2014*

**Precal, please help asap!**

You need to clarify the diagram. Label the airplane A, the tower T and the post P. The plane is at altitude h, with AP=t and AT=p. Point Q is directly below the plane. The distance PQ=q and thus TQ = 2-q. If the plane is between the tower and the post, then h/q = tanα h/(...
*May 26, 2014*

**Algebra, Need help with last part.Thank you**

you are correct on the first two. The last should also be no sweat. There is only 1 2-hearts in the deck of 52 There are 4 twos in the deck. So, how many hearts are there? Also, just as advice, usually you will need to reduce your fractions for your final answers. 4/52 = 1/13 ...
*May 26, 2014*

**algebra 1**

since xy = k is constant, k = (1/2)(-10)
*May 26, 2014*

**maths**

If you mean x = √(y+3) then x^2 = y+3 y = x^2-3 If you mean x = √y + 3 then x-3 = √y y = (x-3)^2 If you mean √x = y+3 then y = √x - 3 It sure helps if you proofread your posts to make it quite clear what's going on. Use parentheses if there is...
*May 26, 2014*

**math**

you know the volume is x*y*z = 12x So, y*z = 12 y cannot be less than 1, so z cannot be more than 12
*May 26, 2014*

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