Thursday

May 5, 2016
Total # Posts: 40,202

**Math **

for the quadratic, note that f(-1) = f(1) = 4 That means the vertex lies on the line x=0. y = a(x-0)^2 + c or, y = ax^2+5 Now use one other point to get a: 1 = 4a+5 a = -1 y = -x^2+5
*April 13, 2016*

**Calculus**

f(x) increases where f'(x) > 0. f(x) is concave up when f"(x) > 0.
*April 13, 2016*

**Math**

brute force way: n + n+2 + n+4 + n+6 = 296 using progressions: 4/2 (2n+3*2) = 296 In either case solve for n, and the next number is n+2
*April 13, 2016*

**Maths**

looks good to me, if all the cricket players also play football.
*April 13, 2016*

**Maths**

A set of n elements has 2^n subsets, including the empty set. So, if you have 4 fillings, and want at least one, that will allow for 2^4-1 = 15 different combinations, using 1 to 4 items. add in the totally plain one, and that gives 16 ways to make the sandwich. (not sand which!)
*April 13, 2016*

**math**

remember that the terms have a constant ratio, so (2k-28)/(k-6) = (k-6)/k Now just solve for k. You will get two answers, only one of which makes all the terms positive.
*April 13, 2016*

**Integers**

or, using what you know about arithmetic progressions, 6/2 (2a+5*1) = 171 a = 26 so the numbers are as shown above.
*April 12, 2016*

**Math**

Medi* comes off before taxes, so 22.48 + 52.72 + 0.23(1625.35-22.48-52.72) = 431.73
*April 12, 2016*

**Math**

just divide the deposit by the total: 175/625 = 0.28 = 28%
*April 12, 2016*

**Math**

well, g(1) = int{1,1} f(t)dt if the integral is done over an interval of zero width, its value is zero.
*April 12, 2016*

**Math**

just subtract the field from the total: (8x)(12x) - (3x)(6x) = 96x^2 - 18x^2 = 78x^2
*April 12, 2016*

**Please HELP! Calculus (Implicit functions)**

or, using implicit, 16x^2 - 8xy - x + y^2 = 0 32x - 8y - 8xy' + 2yy' = 0 (2y-8x)y' = 8y-32x dy/dx = (4-16x)/(y-8x) dx/dy = (√x+4x-8x)/(4-16x) = (1/4)(√x-4x)/(1-4x) Check my math and see whether these agree.
*April 12, 2016*

**Please HELP! Calculus (Implicit functions)**

switch variables and solve for y, and you get (after squaring) 16y^2 - (8x+1)y + x^2 = 0 y = [(8x+1)±√(16x+1)]/32 Pick the branch you want and take the derivative. Using the + branch, y' = 1/4 (1 + 1/√(16x+1))
*April 12, 2016*

**Math**

some kind of exponential would do it. So, with t as time since 1998, f(0) = 72000 f(2) = 70379 f(∞) = 60000 f(t) = 60000 + 12000 e^-kt now we need k so that f(2) = 70379 60000 + 12000 e^-2k = 10379 k = 0.073 So, f(t) = 60000 + 12000 e^(-.073t)
*April 12, 2016*

**try,check,and revise**

If Carly had c, the Rob had c-4. So, c + c-4 = 42 2c = 46 c = 23 So, Carly had 23 and Rob had 19
*April 12, 2016*

**Calculus Help Stuck Part 2?**

or, consider x-64 as the sum of cubes: x-64 = (∛x)^3 - 4^3 so it factors into (∛x-4)(∛x^2+4∛x+16) Now the fraction is just 1/(∛x^2+4∛x+16) = 1/(16+16+16) = 1/48
*April 12, 2016*

**Calculus Help Stuck Part 2?**

(∛x-4)/(x-64) -> 0/0 so try L'Hospital's rule. Then the limit is (1/(3∛x^2) / (1) = 1/(3*16) = 1/48
*April 12, 2016*

**try,check,and revise**

27+3x
*April 12, 2016*

**math**

(1-2i)(1+2i) = 1^2+2^2 = 5 (1-i)(1+i) = 1^2+1^2 = 2 5*2 = 10
*April 12, 2016*

**algebra/math**

surely you have learned how to solve a quadratic equation, or you'd not have been given this exercise. x^2+6x + 9 = 24 x^2+6x-15 = 0 x = (-6±√96)/2 = -3±2√6 clearly, -3-2√6 is less than -3+2√6
*April 12, 2016*

**algebra**

since (a-bi)(a+bi) = a^2+b^2, we have (15-20i)(1+2i) ------------------ (1-2i)(1+2i) = (15-20i+30i-40i^2)/(1^2+2^2) = (55+10i)/5 = 11+2i
*April 12, 2016*

**Math**

well, solve the equation and pick the smaller value. I hope you are not expecting integers.
*April 12, 2016*

**math**

well, (x + 7/2)^2 = x^2 + 7x + 49/4
*April 12, 2016*

**Trigonometry**

draw a diagram. Then it will be clear that your distance x can be found by 1200/x = sin32°
*April 12, 2016*

**Graphs**

The points on f(2x) are half as far from the y-axis as those of f(x)
*April 12, 2016*

**Math**

depends on the shape of the volume, eh?
*April 12, 2016*

**math**

see whether you get what wolframalpha does: https://www.wolframalpha.com/input/?i=solve+%28x-2%29^2+%2B+%28y-7%29^2+%3D+169,+x-2y%3D10
*April 12, 2016*

**math**

all points (x,y) that are 13 units away from the point (2,7) defines a circle: (x-2)^2 + (y-7)^2 = 169 so, the line x-2y=10 may intersect the circle in 0,1, or 2 points. So, plug x=2y+10 into the equation of the circle and see where the two graphs intersect.
*April 12, 2016*

**math**

well, they intersect where f(x) = g(x). x^3-x^2+x+1 = x^3+x^2+x+1 -x^2 = x^2 x = 0 to check, see https://www.wolframalpha.com/input/?i=x^3-x^2%2Bx%2B1+%3D+x^3%2Bx^2%2Bx%2B1
*April 12, 2016*

**Math 142 (Pre-Cal) (Circles)**

the circumference is 2pi*10 = 62.83cm So, multiply that by the number of times the wheel turns in 15 seconds.
*April 12, 2016*

**Math/geometry**

since the angles x and y are complementary, x+y = 90 y = 3x+6 now just solve for x and y.
*April 12, 2016*

**Geometry**

since the circle has area πr^2, and the sphere has surface area 4πr^2, what do you think?
*April 12, 2016*

**Algebra**

A linear equation is y=mx+b where x is the sales, b is the base pay, and m is the percentage used to find the commission. We have 560 = m*800 + b 460 = m*460 + b 540 = m*540 + b 600 = m*1000 + b Those points do not fit any linear equation. Check for typos.
*April 12, 2016*

**Maths Ms sue**

300+10+16+22+... = 310 + 19/2 (2*16 + 18*6) = 1640
*April 12, 2016*

**math**

can you not check your answers? (-4,8) works (5,35) works
*April 12, 2016*

**Geometry - incomplete**

No idea where CDE are in relation to BGF. All you have said is that the two squares share corner A. However, you do know that the smaller square has sides 1/2 as long as the larger one, so its area is 1/4 as big. I suspect you can use that to determine the shaded area. Also, a...
*April 12, 2016*

**Algebra 1**

Who needs a teacher? Just think a bit. Where is the ball to start with? At the top of the cliff. That's when t=0. So, plug in 0 for t and evaluate.
*April 12, 2016*

**math**

they all express a ratio, but I'd guess C is least likely to be used.
*April 12, 2016*

**Math**

can't quite parse your text. It's probably one of 976 + 2n or 9762n
*April 12, 2016*

**Math**

if the angle is x, then it is opposite the shortest side. tan(x) = 5/8
*April 12, 2016*

**Math**

P(blue) = 3/12 * 2/11 P(>= 1 blue) = 1-P(no blue) = 1 - (9/12 * 8/11)
*April 12, 2016*

**algebra. someone please explain to me please!**

since time = distance/speed, d/12 + d/6 = 6
*April 12, 2016*

**Pre calculus**

what about the uphill anchor point? I assume the antenna is vertical. Anyway, if the uphill anchor point is x feet from the base, then we have uphill cable length is u, where u^2 = x^2+100^2 - 2*100x cos 78° downhill cable length d is d^2 = 95^2 + 100^2 - 2*95*100 cos102°
*April 12, 2016*

**algebra**

900 + .07(x-1000) = 2900
*April 12, 2016*

**Basic math**

5ml/4hr * 14days * 24 hr/day * 1floz/29.57ml = 14.20 floz
*April 12, 2016*

**Math Check my Answers please ?**

good work. both correct.
*April 12, 2016*

**Math**

I like C, but it rises 3 ft for every 4 ft of horizontal travel. Double-check the table and the questions. If D says it rises 3/4 ft or 9 inches, then D is your choice.
*April 12, 2016*

**Math**

4^4 * 4^6 = 4^(4+6) = 4^10 you add exponents, since what you are really doing is just short for 4x4x4x4 x 4x4x4x4x4x4 = 4x4x4x4x4x4x4x4x4x4 just as multiplication is short for 4x4 + 4x6 = 4x(4+6) 4+4+4+4 + 4+4+4+4+4+4 = 4+4+4+4+4+4+4+4+4+4
*April 12, 2016*

**math**

a = l*w a = (w+3)(w) = w^2+3w
*April 12, 2016*

**math**

25,10,10,5,5,1
*April 12, 2016*

**math**

(n+3)^2 = 25 n+3 = -5 n = -8
*April 12, 2016*

**Algebra**

Just use the quadratic formula, which you learned in Algebra I: t = -233±√(233^2 - 4(-16)(48)) -------------------------------- 2(-16) t = (233±√57361)/32 or, t = -0.20 or 14.76 We don't allow negative time, so ...
*April 12, 2016*

**Algebra**

it hits the ground, naturally, when h=0. So, just find t when -16t^2 + 233t + 48 = 0
*April 12, 2016*

**Math**

If you bisect the first chord with a radius, you will have a right triangle with sides 15 and 20. So, the hypotenuse (another radius) is 25. Now, draw the second chord, and its triangle is 7-24-25, so the full chord is 14 cm long.
*April 12, 2016*

**Algebra**

x^2-9x+14 = 0 x^2 - 9x + (9/2)^2 = -14 + (9/2)^2 (x - 9/2)^2 = 25/4 x - 9/2 = ±5/2 x = 9/2 ± 5/2 x = 2 or 7
*April 12, 2016*

**science**

if 1/4 remains, that means 2 half-lives have passed.
*April 12, 2016*

**Math**

2x-4 = 2(x-2) 12x-24 = 12(x-2) So, the LCD is 12(x-2), not 24(x-2) (6x+5x) / 12(x-2) 11x/12(x-2) This is the same as your answer, if you cancel a factor of 2 which you did not need in the LCD.
*April 12, 2016*

**word problems**

naturally, when cost = revenue: 32x = 22x+1830 10x = 1830 x = 183
*April 12, 2016*

**math**

since time = distance/speed, d/12 + d/6 = 12
*April 12, 2016*

**Algebra**

you can get an idea of how these things work here: http://davidmlane.com/hyperstat/z_table.html try using your numbers, and you will see shaded areas.
*April 12, 2016*

**Physics**

nove height?
*April 12, 2016*

**math**

70 + 28n <= 1800
*April 11, 2016*

**math investment problem**

.05*4400 + .09x = 697.00
*April 11, 2016*

**Math**

clearly that would be 72/134
*April 11, 2016*

**Business math - question help**

400*1.1^14 + ... + 400*1.1^1 = 400(1.1^15-1)/(1.1-1) = 12709
*April 11, 2016*

**science**

recall that F = ma now plug in your numbers.
*April 11, 2016*

**Math**

mr and mrs smith, their 2 children and fog want to cross a river in a boat that would hold only 80 kg and both mr. amd Mrs Smith have a mass of 80 kg and both the children have a mass of 40 kg and the dog has a mass of 5 kg explain how they can cross the river in the fewest ...
*April 11, 2016*

**Math**

f' = 1 - 3/x^(2/3) = (x^(2/3)-3)/x^(2/3) f'=0 when x^(2/3) = 3 x^2 = 27 x = ±√27 the tangent is vertical at x=0. f increases where f' > 0: (-∞,√27)U(√27,∞) f decreases where f' < 0: (-√27,√27) The graph ...
*April 11, 2016*

**Geometry**

perimeter grows by a factor of 2, area by 4. So, find the existing values and then scale them up.
*April 11, 2016*

**Math**

well, the width is 7 and the height is 1.
*April 11, 2016*

**Math**

clearly the width is 7, since JK is a horizontal line. so the height is 1.
*April 11, 2016*

**Geometry**

I assume you can find the perimeter and area of the original pyramid. if the sides double, so does the perimeter. But the area, since it is the product of two sides, grows by a factor of 2^2, so it is 4 times as big.
*April 11, 2016*

**Math**

If CD=h and BC=x, then h/x = tan24° h/(x+7600) = tan16° or, h = 0.4452x h = 0.2867x + 2179.2649 0.4452x = 0.2867x + 2179.2649 BC = x = 13750 CD = h = 6121
*April 11, 2016*

**Math**

two distinct solutions means that the discriminant is positive. So, we need k^2 - 64 > 0 also, we need (k±√(k^2-64))/4 to be an integer. So, k±√(k^2-64) must be a multiple of 4. and k^2-64 must be an integer. so, what pythagorean triples do you ...
*April 11, 2016*

**Math**

the ball hits the ground when y=0. If you want a fraction, then let's get rid of the decimals: y = 1/10 (-49t^2 + 35t + 50) = 1/10 (7t+5)(10-7t) y=0 when t = 10/7
*April 11, 2016*

**Pre algebra**

6n-8 = 13 + 4(n+3) 6n-8 = 13+4n+12 2n = 33 n = 33/2
*April 11, 2016*

**maths help!??**

since time = distance/speed, 4/9 + x/2 = 1 That will tell you the rest of the distance. I suspect you have garbled your question, since they told you his speed for the first 4km was 9km/hr.
*April 11, 2016*

**Math**

translate up 3 means add 3 to all the y-values. left 3 and up 2 means subtract3 from x and add 2 to y. just think of the axes, and which directions are positive and negative. (4+2 , 3-5)
*April 11, 2016*

**Algebra 2**

tan^4 - sec^4 = (tan^2-sec^2)(tan^2+sec^2) = (tan^2-(1+tan^2))(tan^2+(1+tan^2)) = (-1)(1+2tan^2) = -2tan^2-1 Reiny, imagine the missing x's are present!
*April 11, 2016*

**Math**

the first digit must be 3,5,7 the other digits can be 1,3,5,7,9 since the 1st digit cannot be repeated, that means the last 3 digits must be formed using only 4 of the available choices, giving 4*3*2 choices. So, since the 1st digit can be chosen 3 ways, there are 3*4*3*2 ways...
*April 11, 2016*

**Math**

using the sum of tangents formula, tan(arctan x + arctan y) = tan(arctanx)+tan(arctany) ----------------------------- = tan(pi/4) 1 - tan(arctanx)-tan(arctany) (x+y)/(1-xy) = 1 x+y = 1-xy x+xy+y = 1
*April 11, 2016*

**Factor out the Greatest Common Factor (GCF)**

well, take a look 45d^3 = 9d^2 * 5d 18d^2 = 9d^2 * 2 so, what do you think?
*April 11, 2016*

**maths**

length = w+2
*April 11, 2016*

**Calculus**

check the related questions below. for extrema as described above, you need f' = 3ax^2+2cx = 0 at x=0 and -4, so x(3ax+2c) = 0 -12a+2c = 0 You also have two points, so -64a+16c+d = 9 0a+0c+d = 6 a = 3/32 c = 9/16 d = 6 so, that means that f(x) = 3/32 x^3 + 9/16 x^2 + 6 the...
*April 11, 2016*

**Math**

Remember your Algebra I. The max height is represented by the vertex of the parabola. As with all quadratics, the vertex is at t = -b/2a. So, for #1: t = -122/-32 = 3.8125 seconds use the same logic on #2.
*April 11, 2016*

**Vectors, Math**

Since |B| = 4, B = <4/√2,-4/√2> = <2√2,-2√2> AB = B-A = (2√2-3,-2√2-2)
*April 11, 2016*

**math**

b/a = tan 60° = √3 The ratio of the volumes is thus πb^2a/πa^2b = b/a = √3
*April 11, 2016*

**calculus 2**

What, you don't have any work to show? You can verify your results using the handy calculator at http://keisan.casio.com/exec/system/1392171850
*April 11, 2016*

**fds**

all of them
*April 11, 2016*

**math**

you might show your work, so we could check your method. each dogs eats 3.5/7 = 0.5 kg/day 16 dogs eat 8 kg/day That's 720 kg for 90 days Or, 1584 lbs. That's 63.36 bags I guess it depends on how many days you use for 3 months. 91 days gives 64.06 bags
*April 10, 2016*

**Math geometry**

w/146 = cot 50°
*April 10, 2016*

**Geometry**

you are correct if the "thickness" means the height of the material on the ground.
*April 10, 2016*

**Calculus derivatives**

well does that not mean that dy/dx = -1? Using implicit differentiation, 2x + y + xy' + 2yy' = 0 y' = -(2x+y)/(x+2y) so, you want (2x+y)/(x+2y) = 1 2x+y = x+2y y = x plug that into the original equation and you get x^2 + x^2 + x^2 = 1 x^2 = 1/3 so, at (1/√3,1...
*April 10, 2016*

**Math**

If there are x wheat and y oats, x <= 200 y <= 300 x+y <= 250
*April 10, 2016*

**Math :)**

I'd say high volume, since that minimizes the surface area, making the cube last longer. High surface area (lower volume) means faster cooling, but the cube does not last as long.
*April 10, 2016*

**Calculus**

nope 4x/(x-5) -> 20/0 this is just algebra. Recall your rational functions work? Vertical asymptote at x=5.
*April 10, 2016*

**Math**

If Owen has x and Charley has y, then we are told that x-50 = y+50 (x+100) = 4(y-100) Now just find x.
*April 10, 2016*

**Calculus**

This is just ∫∫∫ dz dy dx using the appropriate limits Unfortunately, the plane 2x+z=3 is a vertical plane, and does not bound a region of the paraboloid.
*April 10, 2016*

**math**

8914*1.0136^t = 15000 t = 38.53 Better check your math.
*April 10, 2016*

**Math**

these are headings, not bearings. I do not get a right triangle. I get an angle of 27+90+27= 144 at the turning point. To get the final location, convert each side to its x- and y-components. Add them up, and you can then get the angle θ using tanθ = y/x and then the...
*April 10, 2016*