Wednesday

January 18, 2017
Total # Posts: 47,946

**Maths**

5/7 as many men, so 7/5 as much time.

*January 5, 2017*

**MATH**

well, p^2+pq-6q^2 = (p+3q)(p-2q) p^2-3pq+2q^2 = (p-q)(p-2q) So, what cancels?

*January 5, 2017*

**maths**

a = 2 pi r l

*January 5, 2017*

**Math**

look at the differences: 2,3,_,_,6

*January 5, 2017*

**Math Calc**

1. Think of f(x) = x^3 2. If f'=0, f does not change. 3. think of f(0). It clearly does not satisfy the MVT on [-1,1] The typos do not help...

*January 5, 2017*

**Math Calc**

clearly it is either 3 or 4. Since 4 is not a choice, 3 seems logical. Now, knowing what you do about cubic curves, and that this one comes down from the left, its first turnaround will be a minimum. So, it will be at x=3. Or, note that f" = -4x+14. f"(3) = 2 > 0...

*January 5, 2017*

**Math Calc**

This is a typical exercise using the chain rule. 2x^2 + y^3 =10 4x dx/dt + 3y^2 dy/dt = 0 Now, using your values, when x=1, y=2. So 4(1) dx/dt + 3(2^2)(3) = 0 4 dx/dt + 36 = 0 dx/dt = -9

*January 5, 2017*

**Math!!!**

recall that if z = x+iy zz* = (x+iy)(x-iy) = x^2+y^2

*January 4, 2017*

**Math**

well, 2mn-16m = 2m(n-8) so what can you do to get from -7n+? to ?(n-8) ?

*January 4, 2017*

**algebra**

p +4- 2 (p-10)> 0 p + 4 - 2p + 20 > 0 -p + 24 > 0 24 > p or p < 24

*January 4, 2017*

**math**

check out your sum-to-product formulas. sin(2A+C)+sin(A+2B) = 2sin((2A+C)/2)cos((A-2B)/2) C = ?-A-B 2A+C = 2A+?-A-B = A-B+? sin (2A+C)/2 = sin(?/2 + (A-B)/2) = cos(A-B)/2 and similarly for the others. Much stuff will cancel out.

*January 4, 2017*

**Math**

h(5)-h(2) -------------- = ? 5-2

*January 4, 2017*

**Mathematical reasoning**

p = rain does not come q = crops are ruined and the people will starve p -> q You have ~q, so ~p (contrapositive) since q = r and s, ~r or ~s = ~q

*January 4, 2017*

**Math**

recall that (x+a)^2 = a^2+2ax+a^2 You have 2a = 16

*January 4, 2017*

**Math**

C and D divide BE into three equal parts. 1.64-(-2.83) = 4.47 4.47/3 = 1.49 So, now you know how much goes in each blank space.

*January 4, 2017*

**Calculus**

x23-5

*January 4, 2017*

**Calculus**

x&sup4;-5

*January 4, 2017*

**Calculus**

x&sup0;¹²³-5

*January 4, 2017*

**Calculus**

x&sup5;-5

*January 4, 2017*

**Calculus**

x^²-5

*January 4, 2017*

**Calculus - incomplete**

Fill in the missing text that did not get pasted

*January 4, 2017*

**Math**

well, sums are not directly related products and quotients, so I think more information is needed. I will note, however, that a product is just a short way to write a sum. 4*3 = 4+4+4 or 3+3+3+3

*January 4, 2017*

**Math**

Note that the two points lie on the same horizontal line: y = -6 Graph that line segment, and it will be clear where the other two points lie, since width+height=13

*January 4, 2017*

**pre Calc**

come on. A vertical line has the same x-coordinate everywhere. Look at the point it passes through. Vertical lines are of the form x=h Horizontal lines are y=k

*January 4, 2017*

**pre calc**

Looks like you need to review your Algebra I... 8x ? 3y + 6 = 0 3y = 8x+6 y = 8/3 x + 2

*January 4, 2017*

**pre Calc**

clearly the slope is -3.5 Now think f=mt+b

*January 4, 2017*

**Number Theory**

4x+7 = 2(mod 15) 4x = -5(mod 15) 4x = 10(mod 15) so, what can x be so that 4x = 5k+10 for some k?

*January 4, 2017*

**precalc**

you know that cos(u) might either decrease or increase, depending on u. surely t/52 increases when t does. !!

*January 4, 2017*

**Math**

x = -2 is a vertical line. So, what is the horizontal line through the point? x = -5 is parallel to x = -2, not perpendicular.

*January 4, 2017*

**Math**

F = ma just add up the vectors, after dividing by the mass.

*January 4, 2017*

**Math**

surely you can graph the lines y = 2/3 x y = -2 y = -3x+1 then just take the pieces you need.

*January 4, 2017*

**Pre Calc**

the slopes must be the same, so (8-1)/(2-a) = (1-6)/(a+2-12) a = 30

*January 4, 2017*

**profit&loss mathematics**

come on. B paid 20% of A's cost: 1.20A C paid what A did: B/1.20 = 08.3333B So, B lost 16.666 % maybe my math looks as funny to you as your texting does to me...

*January 4, 2017*

**profit&loss mathematics**

B = 1.20A C = A = B/1.20 = (5/6)B so, that is ...

*January 4, 2017*

**Maths**

?x^2 h = 800 h = 800/(?x^2) The area is two circles plus a curved cylinder, so a = 2?x^2 + 2?xh the result follows, so just find x such that da/dx = 0

*January 4, 2017*

**mathematics**

sorry - a=20 ! :-(

*January 4, 2017*

**mathematics**

you must be studying geometric sequences, so just note that this is the sum of the sequence with a = 12 r = 3/5 Now just use your formula for the infinite sum: s = a/(1-r)

*January 4, 2017*

**am I right ? or no?**

you are correct that b^x is growth if b>1 and decay if b<1

*January 4, 2017*

**Maths**

convert the area to m^2 area = length*width, so divide by the width to get the length

*January 4, 2017*

**Maths**

0.5ha * (10000m^2/ha) / 12.5m = 400m

*January 4, 2017*

**algebra - duh @Reiny**

It usually helps to read the problem carefully. Nice work, Reiny

*January 4, 2017*

**algebra**

x+y <= 9x-5y 6y <= 8x 3y <= 4x You might also want to consider x+y <= |9x-5y|

*January 4, 2017*

**Maths**

n = d-7 (n+2)/(d+9) = n/d (d-7+2)/(d+9) = (d-7)/d d(d-5) = (d-7)(d+9) d^2-5d = d^2+2d-63 7d = 63 d=9 check: original fraction: 2/9 modified fraction: 4/18 = 2/9

*January 4, 2017*

**Maths**

if you have a unix system, you can use the bc calculator for arbitrary precision, as well.

*January 4, 2017*

**Math**

1/4 of 2 cups is ??

*January 4, 2017*

**math**

((3200/1.60)/4)^2 * 1.20/100 = 3000

*January 4, 2017*

**Math**

there are 4 choices for each digit, so 4^4 total ways. 3/4 of them start with a number less than 7, right?

*January 4, 2017*

**Math;);)**

the two points lie on the unit circle, clearly 54-19 degrees apart. The angle is 35°. or, use the distance formula to find the vector u-v. Then use the law of cosines to find the included angle.

*January 4, 2017*

**math**

Just plug in n=5: a5 = 6*5-4 = ?

*January 3, 2017*

**Math**

well, the equations is (x-(2-3i))(x-(2+3i)) = 0 ((x-2)+3i)((x-2)-3i) = 0 (x-2)^2 + 3^2 = 0 x^2-4x+4 + 9 = 0 x^2-4x+13 = 0 a+b = -4+13 = 9

*January 3, 2017*

**Math**

try using letters like a,b,c instead of the special characters that are getting mangled.

*January 3, 2017*

**maths**

if x<0>=0 then 4/(x<0>)^2 is undefined. I'll assume that x<n+1> = 4/(x<n>^2+5) If so, then x<0> = 0 x<1> = 4/(0^2+5) = 4/5 = 0.8 x<2> = 4/(0.8^2+5) = 4/5.64 = 0.7092 ... The actual root ? 0.72408 If I got the formula wrong, then ...

*January 3, 2017*

**maths**

areas grow as the square of the linear factor. So the areas are A:B = (8:10)^2 = 64/100 = 16/25 A/160 = 16/25 A = 16*160/25 = 102.4 cm^2

*January 3, 2017*

**math**

tan(x) = h/d = 4d/d = 4 x = arctan(4) = 76° for part b, h decreases, because x decreases.

*January 3, 2017*

**math**

3^-n = 0.2 3^n = 1/0.2 = 5 (3^4)^n = (3^n)^4 = 5^4 = 625

*January 3, 2017*

**Maths**

V = 4/3 ? r^3 A = 4? r^2 = 3V/r = ?(36?V^2) Now just plug in your numbers.

*January 3, 2017*

**Algerbra**

He will need (253.5/6)^(3/2) * 2 = 549.25 kg of clay So, he will need 55 10kg bags

*January 3, 2017*

**Surfaces of cones**

?r?(r^2+h^2) = 2160? (12x)?(144x^2+256x^2) = 2160 (12x)(20x) = 2160 x^2 = 9 x = 3 so, the volume is ?/3 r^2h = (?/3) (24*3)^2 (16*3) = 82944? V = 82944 cm^3

*January 3, 2017*

**Maths**

just expand the left side. It will be the same as the right side. One way to start would be (3x-1)(x+5)(4x-3) = 3x(x+5)(4x-3)-(x+5)(4x-3) Now, (x+5)(4x-3)=4x^2+17x-15 so you can proceed with = 3x(4x^2+17x-15)-(4x^2+17x-15) = ...

*January 3, 2017*

**Math**

sorry - only one equation.

*January 3, 2017*

**Math**

useless problem. 6 apples - 2 oranges =

*January 3, 2017*

**Math**

Q = 10-P so, P^2-Q^2 = 40 P^2-(10-P)^2 = 40 20P-100 = 40 20P = 140 P = 7 So, Q = 3 check: 7^2-3^2 = 49-9 = 40

*January 3, 2017*

**algebra(difference of two squares)**

Your answer is clearly incorrect, since you want integers. The problem is that odd numbers differ by 2, so (n+2)^2-n^2 = 336 now it should work better.

*January 3, 2017*

**Math**

T = k?L using L'=1.4L instead, we have T' =k?L' = k?(1.4L) = k?L ?1.4 = T?1.4

*January 3, 2017*

**trigonomentry hope steve or damon reiny can help**

Lat's just use u and v for ease of typing x = cosu + i sinu y = cosv + i sinv (x-y)/(x+y) = (cosu-cosv) + (sinu-sinv)i ------------------------------- (cosu+cosy) + (sinu+siny)i Now multiply top&bottom by the conjugate of the denominator, collect terms, and recall that tan...

*January 3, 2017*

**Maths**

AB = 2x = 1.7 CD = 3x = 2.55 BD/CD = tan52° BD = 2.55 tan52° = 3.264

*January 3, 2017*

**math**

1800/1350 * 3

*January 3, 2017*

**MATH**

3:9

*January 3, 2017*

**Math**

If n were nabbed, then letting j = the jaywalkers, we have n/4 = j Now go on to the next sentence...

*January 3, 2017*

**Math**

well, check the differences: 1-1=0 4-3=1 9-7=2 16-13=3 25-21=4 So, how does that relate to n?

*January 3, 2017*

**Mathmatics**

If the two numbers are n and n+1, then we have (n+1)^2 - n^2 = n^2+2n+1-n^2 = 2n+1 = n + n+1

*January 3, 2017*

**Math (please check my answer!!)**

correct

*January 3, 2017*

**math**

looks good to me. S=131 L=452 = 2*131+190 = 131+321

*January 3, 2017*

**Math**

I suspect it was 30 by 20 to start with.

*January 3, 2017*

**Maths**

but yes, you are in fact correct.

*January 3, 2017*

**Maths**

huh? a,b,c are the coefficients in the equation, as usual!

*January 3, 2017*

**Math**

Reiny's answer is correct, according to (1 + x/(1-x) / (1 - x/(1-x) ) The domain is all reals except x = 1/2 or 1 Even though the domain of 1/(1-2x) only excludes x = 1/2, we also need to exclude x=1 since f(1) and g(1) are undefined, so f(g(1)) cannot be defined either.

*January 3, 2017*

**math coordinate geometry**

fix what's missing and maybe we'll give it a shot.

*January 3, 2017*

**maths**

tanx+tan2x+?3tanx tan2x=?3 tanx+tan2x = ?3 - ?3tanxtan2x tanx+tan2x = ?3(1-tanx tan2x) (tanx+tan2x)/(1 - tanx tan2x) = ?3 tan3x = ?3 ...

*January 2, 2017*

**Math**

(x+1)^3 = ?(x^2)

*January 2, 2017*

**math**

yes

*January 2, 2017*

**science**

Looks more like B and C to me. It takes force to turn the turbines. The weight of the water is force. The height it falls increases the momentum of the water, which is transferred to the turbines. Water which is not flowing (falling) exerts no force to turn the turbines.

*January 2, 2017*

**Math**

100000*(56/100)^(t/(2010-1990)) massaged as needed

*January 2, 2017*

**trigonomentry ps**

oh, yes. x=3?/2 also works.

*January 2, 2017*

**trigonomentry**

you can rewrite it as sinx + cosx + cos^2(2x) = 0 clearly x= 3?/4, ?, 7?/4 are some solutions. To find them all will take some doing. working with our equation, -sinx = cos^2(2x) + cosx square both sides to get sin^2(x) = cos^4(2x) - 2cos^2(2x)cos(x) + cos^2(x) 1-cos^2(x) = (...

*January 2, 2017*

**Algebra**

(x+1)^3 = ?(x^2)

*January 2, 2017*

**Math**

50+10m

*January 2, 2017*

**algebra**

2x-2 < -12 2x < -10 x < -5 2x+3 > 7 2x > 4 x > 2 So, x < -5 or x > 2 Work the other in like wise. Just clear the fractions first to make things easier.

*January 2, 2017*

**integral calculus**

see Mycah's post below

*January 2, 2017*

**business maths**

a worthy goal, to be sure.

*January 2, 2017*

**SAT MATH**

Line m has slope -3/8. So, using the point-slope form, y-(r-2) = -3/8 (x-r) or, 3x+8y = 11r-16 Now solve that along with 8x-3y=n and set the intersection to be (r,r-2). Then solve for r in terms of n.

*January 2, 2017*

**integral calculus**

Hmmm. I get x/2 - sin(2x)/4

*January 2, 2017*

**Add math**

?((x-4)^2+(y-8)^2) = 2?((x+2)^2+(y-3)^2) square both sides and collect terms. It will be a circle. http://www.wolframalpha.com/input/?i=circle+((x-4)%5E2%2B(y-8)%5E2)+%3D+4((x%2B2)%5E2%2B(y-3)%5E2)

*January 2, 2017*

**Add math**

1+y+1+2y+2+13+16 = 6*9 Find y, then get ?^2 as usual.

*January 2, 2017*

**Add math**

max area when square. So, 12x = 4-x

*January 2, 2017*

**Add Math(rate of change)**

v = ?r^2h dv/dt = 2?rh dr/dt + ?r^2 dh/dt Now just plug in your numbers to get dr/dt Note that since h=2r, dh/dt = 2 dr/dt Or, since h=2r, v = ?r^2h = 2?r^3 dv/dt = 6?r^2 dr/dt

*January 2, 2017*

**Analytic Geometry**

the slope is 1. So, the line is y = x+1

*January 1, 2017*

**mathematics**

a + a+d = 4 a+9d = 19 a+4d + a+5d = ?

*January 1, 2017*

**calculus-add**

see your earlier post for #1 For #2, review your techniques for 1st order linear ODEs, and see whether you can get the solution given here: http://www.wolframalpha.com/input/?i=(x-2)+dy%2Fdx+%3D+1-3y(x-1)%2F(x%2B1) Solve the homogeneous equation using partial fractions, and ...

*January 1, 2017*