Friday

October 9, 2015
Total # Posts: 34,460

**Math**

If you're taking square roots, the number must be a perfect square to give a rational root. 64 = 8^2, so √64 = 8 is rational Similarly, since 64 = 4^3, ∛64 = 4 is rational. For small numbers, it's easy to check for possible roots, as there aren't that ...
*October 7, 2015*

**math**

40 men @ 8 hrs/day = 320 man-hrs/day 60 men @ 6 hrs/day = 360 man-hrs/day So, it will take 320/360 = 8/9 as long, or 80/3 days
*October 7, 2015*

**Calculus 1**

for a sphere, a = πd^2 da/dt = 2π dd/dt -6 = 2π*11 dd/dt So, dd/dt = -3/(11π) cm/min
*October 7, 2015*

**math**

3+4+5 = 12 360 = 12*30 that should help
*October 7, 2015*

**math**

first off, what is standard form? Those look pretty standard to me already.
*October 7, 2015*

**physics**

s = 3.2t + 1/2 at^2 3.2(3.3) - a/2 (3.3^2) = 16 a = 1.0 so, a = 1/9.8 g So, sin(theta) = 1/9.8 theta = 5.86 degrees
*October 7, 2015*

**math**

well, the sets of three factors of 48 are 1,1,48 1,2,24 1,3,16 1,4,12 1,6,8 2,2,12 2,3,8 2,4,6 3,4,4 Looks like the 10th student will have to duplicate one of those solids.
*October 7, 2015*

**Calculus**

Okay. If the man is x meters from the pole, and his shadow's length is s meters, then using similar triangles, we have (x+s)/5 = s/1.7 So, that means that x = 5s/1.7 - s or, s = 0.51x So, ds/dt = 0.51 dx/dt = 0.51*1.6 = 0.82 m/s
*October 7, 2015*

**Simultaneous equation**

well, using the values 1,3,5 how can you make them add up to 1 if not all are positive?
*October 7, 2015*

**Simultaneous equation**

well, if we want integer solutions, it is clear that not all the values can be positive. However, squares are positive, and we know that 1^2+3^2+5^2 = 35 You will need to make one or two of the variables negative, so you sum to 1, but that should work for the cubes as well.
*October 7, 2015*

**MATH HELP PLEASE**

k(x) = (x−1)^2 − 6 Clearly the vertex is at (1,-6), The x-intercepts are not integers, The y-intercept is at (0,-5) So, pick any integer value except 0 or 1 for x, and plug it in! k(-1) = -2 k(10) = 75 k(-100) = 10195 You can use decimal or irrational values as ...
*October 7, 2015*

**6th Grade Math**

If there were x boxes at $2, the rest (35-x) were $3 boxes. So, add up the sales for everything: 2x+3(35-x) = 92
*October 7, 2015*

**math**

since the relationship is proportional, the distance d and the time t are related by d = kt where k is a constant. So, if you double the time, you have k(2t) = 2(kt) = 2d so, the distance also doubles. Or, you can think of it like this. d/t = k, a constant If you now have 2t, ...
*October 7, 2015*

**Algebra**

Well, you did some calculations (some of them incorrect), but at the end, you didn't even come close to answering the question that was asked. k(x) = (x−1)^2 − 6 Clearly the vertex is at (1,-6), The x-intercepts are not integers, The y-intercept is at (0,-5) So...
*October 7, 2015*

**Math**

if the differences are constant, the sequence is arithmetic. They are 1,2,3,4 So, the sequence is not arithmetic. If the ratios are constant, the sequence is geometric. They are 3/2, 5/3, 8/5, 3/2 So, the sequence is not geometric either.
*October 7, 2015*

**math**

0x3 + 18x1 1x3 + 15x1 2x3 + 12x1 ... 6x3 + 0x1
*October 7, 2015*

**maths**

(6/2)(2a+5d) = 6 (a+d)(a+4d) = -80 or, 2a+5d = 2 a^2+5ad+4d^2 = -80 Now just solve for a and d. One sequence is -14, -8, -2, 4, 10, 16 sum = 6 (-8)(10) = -80 There is another value for a as well
*October 7, 2015*

**Angle of depression need help also**

if the angle of depression is decreasing, then the plane is flying away from the platform. 30s * 600km/hr * 1hr/3600s = 5km So, if you draw a diagram, you can see that if the plane's height is h km, h cot45° - h cot60° = 5
*October 7, 2015*

**What must be added maths need help**

if the needed amount is z, then x/y + z = y/x z = y/x - x/y You can massage that into other forms if you like. Not sure why this caused you trouble. If I ask what needs to be added to 6 to make 10, you naturally say 10-6 = 4 right?
*October 7, 2015*

**Maths**

cubics are not simple to solve, in general. Descartes' Rule of Signs says that there are no negative roots. I suggest a graph or Newton's method for finding the roots. What methods have you studied? f(0) = -2.4 f(1) = 3.49 f(3) = 3.0 f(4) = -0.9 f(10) = -1.08 f(11) = ...
*October 7, 2015*

**Calculus 1**

after t hours, car One has traveled 40t miles car Two has traveled 30t miles Using the Pythagorean Theorem, the distance between the cars is 50t miles. Looks like the distance is growing at a constant 50 mi/hr. No calculus even needed.
*October 7, 2015*

**algebra**

the values to be excluded from the domain are those which make the denominator zero, since division by zero is undefined. so, where is 8x(x-1) = 0?
*October 7, 2015*

**Math**

so, how does your chart look? I assume you have bands of various widths, in various colors.
*October 7, 2015*

**Holy Batman!**

40000*1.16^3
*October 6, 2015*

**Math**

where is 8x^2-8x = 0?
*October 6, 2015*

**algebra 1**

If the son takes x hours, 1/7 + 1/x = 1/4
*October 6, 2015*

**Word problems**

since the height y is given by y = 5.0 + 10.5t - 4.9t^2 just solve for t in 5.0 + 10.5t - 4.9t^2 = 0
*October 6, 2015*

**Algebra**

Ah, but divide by what? If there are r rows, each row has r+9 seats. So, r(r+9) = 1960 r^2+9r-1960 = 0 factors of 1960 are many, but two which differ by 9 are 40 and 49. So, (r+49)(r-40) = 0 There are 40 rows of 49 seats.
*October 6, 2015*

**Pre-algebra**

because the slope of a vertical line is undefined.
*October 6, 2015*

**Math**

Sort of, but murkily. Since the players can be divided into groups of more than one player each, the size of the groups is a divisor of the number of players. So, not prime.
*October 6, 2015*

**adv functions**

-6-√2 <x< -6+√2 -√2 < x+6 < √2 (x+6)^2 < 2 x^2 + 12x + 36 < 2 x^2 + 12x + 34 < 0
*October 6, 2015*

**math**

just take the reciprocal. hr/gal = 1 / (gal/hr)
*October 6, 2015*

**Music**

Bzzzt. Try C
*October 6, 2015*

**Music**

I think I prefer tempo, which describes how fast the music is. Notation just describes how it is written; nothing about the actual music. The others are musical terms, but are not parameters of the music itself.
*October 6, 2015*

**Geometry**

(-2,-1) -> (-2,-9) -> (4,-9)
*October 6, 2015*

**math- 165 calculas**

Of course x=9 is incorrect. If you cut off a 9" corner from the 18" square, the volume is zero! Probably not the maximum value. dv/dx=0 at another value of x. Use that one.
*October 6, 2015*

**math- 165 calculas**

v = x(18-2x)^2 = 4x^3-72x^2+324x Now just find where dv/dx=0 and that will be the maximum (or minimum!) volume. I'm sure you will be able to tell which one.
*October 6, 2015*

**Math (Algebra)**

The scores were the same, so 18m+19 = 15m+31 Now solve for m, the # points for each multiple-choice question.
*October 6, 2015*

**math- 165 calculas**

here the fraction approaches 5x^2/7x^3 = 5/7x -> 0 If the denominator has higher degree than the numerator, the horizontal asymptote is always y=0.
*October 6, 2015*

**math- 165 calculas**

since the numerator is of higher degree than the denominator, there is no horizontal asymptote. As x gets huge, the lower powers become insignificant, and the fraction approaches x^3/x^2 = x So, there is a slant asymptote, but ho horizontal asymptote. The graph is at http://...
*October 6, 2015*

**Algebra**

clearly, the scale is (10 in):(150 ft) = (10 in):(150*12 in) = 1:180
*October 6, 2015*

**physics**

surely your text (or google!) gives an explanation of how to work with circuits and resistors. Do you have some particular problem, which the concepts can be used to solve? The basic principle is that for resistors in series, the current is the same for all of them. for ...
*October 6, 2015*

**Pre Calculas**

#7 since 0<1, f(0) = 0^2 = 0 #8 double the 1st and your system becomes 6x-2y=0 5x+2y=22 Now eliminate y by adding the two equations. #9 If you try elimination here, you get: 24x-6y=15 -24x+6y=14 Can you see that there is no solution to this system?
*October 6, 2015*

**trigonometry**

You have a nice equation. Is there something we're supposed to do with it? As I recall, w represents the width of a river, and you have the angles at A and B. What is there that you cannot do? Just plug in the values of A and B, and the evaluate the numbers to get w!
*October 6, 2015*

**MATH**

or, equivalently, since the numerator is 2(2x+4) r = (2x+4)/(5x+1)
*October 6, 2015*

**Physics**

speed: (130+65)m/(16.0+4.3)s = 9.61 m/s velocity: (130-65)m/(16.0+4.3)s = 3.20 m/s
*October 6, 2015*

**math**

well, Manny is now 18, so ...
*October 6, 2015*

**maths**

yadda yadda yadda. The equations say it all. The words are redundant. If runner 1 passes runner 2, their distances are equal: 0.2t(t-5.1)(t-9.1) = 2.4 + 0.75t t ≈ 10.1 Check out the graphs at http://www.wolframalpha.com/input/?i=0.2t%28t-5.1%29%28t-9.1%29+%3D+2.4+%2B+0.75t
*October 6, 2015*

**pre-cal**

since we have real coefficients, and 2i is a root, so is -2i. If 1/2 is a root, one factor of p(x) is (2x-1). So, p(x) = (2x-1)(x-2i)(x+2i) = (2x-1)(x^2+4)
*October 6, 2015*

**math**

recall the law of cosines, and you will see that θ can be found using 38^2 = 30^2 + 27^2 - 2(30)(27)cos(π-θ)
*October 6, 2015*

**Math**

well, you have 5*4 = 20 How many more to get 30?
*October 6, 2015*

**Algebra**

if they traveled x hours at 20 mi/hr, then they went (260-20x) miles at 70 mi/hr Since time = distance/speed, (260-20x)/70 + x = 9 x = 7.4 check: they traveled 1.6 hr * 70 mi/hr = 112 mi 7.4 hr * 20 mi/hr = 148 mi Total: 260 mi
*October 6, 2015*

**Calculus/Math**

you have (1-2x)/(√(1+x^2)-1) multiply top and bottom to get (1-2x)(√(1+x^2)+1) / (√(1+x^2)-1)(√(1+x^2)+1) = (1-2x)(√(1+x^2)+1)/x^2 = (1-2x+√(1+x^2)-2x√(1+x^2))/x^2 = 1/x^2 - 2/x + √(1/x^4+1/x^2) - 2√(1+1/x^2) as x→&#...
*October 6, 2015*

**MATH**

7(4z-3) > 59 28z - 21 = 59 28z > 80 z > 20/7
*October 6, 2015*

**jms**

exponents first
*October 5, 2015*

**Physics**

A+AB = A(1+B) = A(1) = A (A+B)(A+C) = A(A+C)+B(A+C) = A+AB+BC = A+BC
*October 5, 2015*

**Calculus 1**

well, just plug in some numbers! f(0) = 10, so a/(1+b) = 10 df/dt = a(0.5be^(-0.5t))/(1+be^-0.5t)^2, so a(b/2)/(1+b)^2 = 4 Solve those two equations, and you get a = 50 b = 4
*October 5, 2015*

**Geometry**

well, just draw angle ABC. Then pick a point D somewhere between B and C, and draw the ray BD. Then you have (7x-9)+(5x-6) = (5x+6) ABC is the big angle. ABD + DBC = ABC
*October 5, 2015*

**Algebra**

You want x where 0.046x + 0.10(6500-x) = 1000
*October 5, 2015*

**Combination and Permutation**

Clearly, that is 52C2 Doesn't matter whether the deck is shuffled or not. Same 52 cards!
*October 5, 2015*

**Math**

the two-point form of the line is y+5 = -9/4 x now just rearrange things as needed.
*October 5, 2015*

**Math**

well, just plug in the point: 3(-5)-3(6)+2 = -15-18+2 = -31 so, 3x-3y+2 = -31 3x-3y+33 = 0 x-y+11 = 0
*October 5, 2015*

**math**

use s = rθ
*October 5, 2015*

**geometry**

(-2,-1) -> (-2,-9) -> (4,-9)
*October 5, 2015*

**Geometry**

assuming that ABCDE are points in that order, draw the line and mark 'em off. AB=BC CD=DE AE = AB+BC+CD+DE = AB+AB+DE+DE = AB+AB+AB+AB = 4AB
*October 5, 2015*

**math**

just look up the formula for the area of a segment of radius r and angle θ: a = 1/2 r^2 (θ-sinθ) Now plug in r=3 and θ=π/3
*October 5, 2015*

**precalc**

32 cos 32°
*October 5, 2015*

**Math (Trig)**

I think you should apply the angle bisector theorem here, since AD bisects angle ABE and AE bisects angle ADC.
*October 5, 2015*

**Mathematics**

sorry. can't be done with elementary functions. Better use Newton's method or graph it and read the solution.
*October 5, 2015*

**geometry**

well, seems to me you just need to do the construction and try the step you think will work.
*October 5, 2015*

**Math**

It is in scientific notation. I guess standard form would be found by shifting the decimal point 5 places to the left: 0.0000356
*October 5, 2015*

**math algebra**

just keep track of all the costs involved: 1.80x + 2.60(20) = 2.12(x+20)
*October 5, 2015*

**8th grade geometry**

If your answer is correct, you made a typo in the 1st point of the problem. If two of the vertices are (3,-2) and (-3,-2) then the base is clearly a horizontal line. So, any point 3 units above the base will produce the desired height. That would be (x,1). (0,1) is the point ...
*October 5, 2015*

**Calculus**

As always, draw a diagram. Using similar triangles, the man's shadow height h when he is at a distance x from the light, is given by 2/x = h/12 or, hx = 24 So, when the man is 4m from the wall (8m from the light) 8h=24, h=3 x dh/dt + h dx/dt = 0 Now plug in your values: 8 ...
*October 5, 2015*

**Math in Science**

42
*October 5, 2015*

**math**

in years, d = j+3
*October 5, 2015*

**Math**

15x-20 <= 130 15x <= 150 x <= 10
*October 5, 2015*

**Algebra**

not sure what 2Ex<33 means, but it has something to do with integers less than 33.
*October 5, 2015*

**Pre Calculus**

#1 in a linear function, equal spacing in x produces equal spacing in y. The ratio is called the slope, and is constant. Only table #3 meets that condition. #2 A function whose domain is [2, infinity): √(x-2) An arithmetic sequence: 1,2,3,4,... A system of equations with...
*October 5, 2015*

**Geometry help**

it appears that angles 1 and 2 form a straight line, so their sum is 180°.
*October 5, 2015*

**Physics**

these all just use the Pythagorean Theorem, or the distance formula, which is the same. Just figure out the final location, and then use the formula. For #1, (0,0) -> (-10,0) -> (-10,-10) distance is √(10^2+10^2) = 14.1
*October 5, 2015*

**History**

Your parents own their own business and they do very well financially. They are very independent and take responsibility for all their own business and personal costs. based on this information which political party are your parents a member of? My answer is Republican Party
*October 5, 2015*

**Math help please?! :)**

(4x10^3)(6x10^6) = (4x6)x(10^3 x 10^6) = 24x10^9 but that is not SN. You need 2.4x10^10 profit is income less cost. In this case, since the same number of shares were bought and sold, just multiply 15 by the difference in prices: 15(20.375-14.875) = 15(5.50) = 82.50 because he...
*October 5, 2015*

**Geometry Check please**

since only multiplication was used, I'd say that's a good guess... Unless you like dividing by 1/2 ...
*October 5, 2015*

**Geometry Check please**

Answers are good. Typing, not so much . . .
*October 5, 2015*

**Math**

|n| is just the distance from n to zero. n can be to the left of 0 or to the right of 0. |-3| = 3 because -3 is 3 units away from zero. -3 is to the left of 0, +3 is to the right, but in either case. |-3| = |+3| = 3 Get out your number line and try plotting some points. And ...
*October 5, 2015*

**Math; PLEASE CHECK MY ANSWERS**

1C 2D ok 3 B and C are both greater. Typo? If you meant 5.5x10^7, then just B
*October 5, 2015*

**math, mechanics**

Well, if F is dU/dr, and U is a function of r, then there will certainly be r in the answer. But, you want F(r) at r=r0, so geez, just plug in r0! Am/r0^(m+1) - Bn/r0^(n+1) There are other ways of expressing that, but that's another exercise.
*October 5, 2015*

**math, mechanics**

still looking for what F is.
*October 5, 2015*

**History**

thank you
*October 5, 2015*

**History**

I think a
*October 5, 2015*

**History**

What is a key element of democracy? a- self-determination b- selfishness c- violent d- heredity My answer would be a or b
*October 5, 2015*

**math**

either (7/5 * 60) or (7/2 * 60) depending on who got the $60.
*October 5, 2015*

**Language Arts (- Ribbons -)**

∫C (2z-3)/[(z^2-4)(z+2)] dz
*October 5, 2015*

**Math**

this keeps cropping up. See the related questions below. But, just follow the rules you have learned: -12 / 3 * (-8 + (-4)^2 - 6 ) + 2 -12 / 3 * (-8 + 16 - 6 ) + 2 -12/3 * 2 + 2 -4 * 2 + 2 -8 + 2 -6
*October 5, 2015*

**Math**

since 3/4 * 1 = 3/4 3/4 * 4/3 = 1 multiplying 3/4 by any number between 1 and 4/3 will work. Or, a little more formally, 3/4 <= (3/4) x <= 1 1 <= x <= 4/3
*October 5, 2015*

**Math help**

If there are x bargain boxes and y deluxe boxes, you want to maximize p = 4x + 6y where 4x+9y <= 300 8x+3y <= 400 Now use your favorite solution method or tool, and you find max p when x=45 y=13 http://www.zweigmedia.com/RealWorld/LPGrapher/lpg.html is a nice tool. It ...
*October 5, 2015*

**Geometry**

reflection through the line y=x moves (x,y) -> (y,x) So, it looks like C with a typo. I mean, geez, did you try actually plotting a point and seeing what happened if you flipped it over the line y=x? or maybe googling reflections? http://www.regentsprep.org/regents/math/...
*October 5, 2015*

**MATH 115 PRE-ALGEBRA**

Just use the distributive property to get rid of the parentheses: 6(3m-7)-2(12y-5)+4(y+6) 6(3m)-6(7)-2(12y)-2(-5)+4(y)+4(6) 18m-42-24y+10+4y+24 Now you can use the commutative property to rearrange things: 18m-24y+4y-42+10+24 18m+y(-24+4)-8 18m-20y-8 If that m was really ...
*October 5, 2015*