Friday

April 29, 2016
Total # Posts: 40,000

**Science**

zero it is back where it started
*March 9, 2016*

**Biology**

The Hershey-Chase experiment proved that DNA was the hereditary material because a- radioactive phosphorus in viral proteins was shown not to enter bacterial cells. b- radioactive phosphorus in viral DNA was shown to enter bacterial cells. c- radioactive sulfur in viral ...
*March 9, 2016*

**6th grade Math**

any amount of blue with yellow will produce some kind of green. No idea how to make it glow...
*March 9, 2016*

**math**

well, there are 2π radians in a complete circle.
*March 9, 2016*

**Algebra**

what do you have against actual math symbols!?!?!? And you have a typo. I suspect you mean 10w^2 - 19w - 15 This kind of thing takes experience and patience. You need to play around with factors of 10 and 15 till you get -19 in the middle. (5w+3)(2w-5)
*March 9, 2016*

**CALC HELP!**

y = x + 4/x y' = 1 - 4/x^2 y'(4) = 1 - 4/16 = 3/4 Now you have a point and a slope, so the line is y-5 = 3/4 (x-4) y = 3/4 x + 2 Looks like you need to brush up on your Algebra I. In the future, if you get stuck, show some of your work, so we can poke holes in it! :-)
*March 9, 2016*

**Algebra**

3g^2 - 7g + 2 (3g-?)(g-?) The only factors of 2 are 1 and 2. So, how can you place them to get -7 in the middle?
*March 9, 2016*

**Trig - Ambiguous Cases**

Your math is correct. The text is wrong. If one angle is obtuse, there can be only one solution. Or none, if the conditions preclude it, as in this case. I suspect a typo in the problem.
*March 9, 2016*

**Please help math!**

what do you mean by an angle "points southwest"? If they share a common side (extended), then they are vertical angles.
*March 9, 2016*

**math help please**

planes that intersect only one of the edges are triangular. Planes that contain two of the edges have quadrilateral cross-sections. If the plane is parallel to one of the base edges, the section is a trapezoid. Otherwise, it is just a general quadrilateral. Try drawing some ...
*March 9, 2016*

**Math**

As n increases by 1, the terms increases by 12. That means that if you add n to the term number, you add 12n to the value. So, start with Tn = 12n But T1=18, not 12. So, you need to add 6: Tn = 12n+6 Or, you can use the general formula for an arithmetic progression with first ...
*March 9, 2016*

**Math**

since 5 and 13 share no factors, they must be 5*13 = 65 people.
*March 9, 2016*

**math**

x + 38*12 <= 1200
*March 9, 2016*

**math**

there are 3 pairs of rectangular faces. The area of a rectangle is length * width. So, add 'em up.
*March 9, 2016*

**Math**

acceleration means change in velocity, either in speed or direction. 0 is a perfectly good velocity. So, what do you think now?
*March 9, 2016*

**Analytical Geometry**

This is quite a general topic, not really suitable for discussion here. Google is your friend. I'm sure you cam find lots of illuminating essays. One of the best works is Mandelbrot's book The Fractal Geometry of Nature
*March 9, 2016*

**Number Theory**

just borrow, making FFFFF<10>. across the top. The result would then be 729585
*March 9, 2016*

**Number Theory**

well, using base 10 for now, if the number has base7 digits abc, we need 49a+7b+c = 81c+9b+a c = 3a/5 - b/40 40c = 24a-b If c=1, a=2,b=8 Nope If c=2, a=4,b=16 Nope If c=3, a=5,b=0 5037 = 3059 check: 49*5+3 = 81*3+5 yes
*March 9, 2016*

**Number Theory**

If you mean 3.4444... base 13, that would be 3 4/12 = 10/3 In base n, the fraction .1111111... is 1/(n-1)
*March 9, 2016*

**Trigonometry**

try using the identity sec^2 x = 1 + tan^2 x It should get you through most of these
*March 9, 2016*

**Geometry**

first, review the point-slope form. It relies on the fact that the slope of a line is constant. So, the slope between any two points is always the same. So, pick any point (x,y) on the line and use the definition of the slope to see that (y-(-1))/(x-6) = 4 Or, more usually it ...
*March 9, 2016*

**math**

just mark each point on the number line. Then it will be clear.
*March 9, 2016*

**math**

4+8x+2.2-10x use the commutative property of addition to rearrange things a bit: 4+2.2 + 8x-10x for the rectangle, area = width * length, so it would be 7(x+2)
*March 9, 2016*

**Math**

#1 nope. what do you have to subtract each time? #4 just substitute numbers for n: Tn = 3n+5 T1 = 3*1+5 = 8 at this point, only one choice remains. But, you can verify the other terms: T2 = 3*2+5 = 11 T3 = 3*3+5 = 14 and so on #5 huh??? see all those 9's? Take another look...
*March 9, 2016*

**University of makati**

work = force * distance so, what is the force pushing down on the ball? what is the height it is being raised? try using google to find similar problems.
*March 9, 2016*

**Math**

well, each meter is 1000 mm
*March 9, 2016*

**Pre calc quadratic stuff**

as with all polynomials, the domain is (-∞,∞) area = 72-2(x-4)^2 You can see that its maximum value is at x=4, since then (x-4)=0 and nothing is subtracted from 72. So, the range is (-∞,72]
*March 9, 2016*

**flowchart and psuiodocode**

input n max=min=n for i=2..6 read n if n>max then max=n if n<min then min=n next i print max,min
*March 8, 2016*

**MATH.**

f = 6x+10 f-10 = 6x (f-10)/6 = x = f^-1 g = 15x^2-8 g+8 = 15x^2 (g+8)/15 = x^2 √((g+8)/15) = x = g^-1 I'm sure you can handle the last one, right?
*March 8, 2016*

**math**

as always, draw a diagram. Review the cot function. The distance is 245 cot35° - 245 cos42°
*March 8, 2016*

**math**

0.0125x^2 - x = 1/80 x^2 - x = 1/80 (x^2 - x + 1/4) - 1/80 * 1/4 = 1/80 (x - 1/2)^2 - 1/320 max depth is 1/320 cm
*March 8, 2016*

**math**

The polygon is divided into 30 isosceles triangles, with vertex angle 360/30 = 12° So, now you have 60 right triangles with one angle 6° and hypotenuse 9mm So, the base of each triangle is 9sin6°, and the height is 9cos6°. The total area is thus 60 * (1/2)(...
*March 8, 2016*

**Math**

as always, draw a diagram. The distance d between the house and pole is d = 8cot42° Now you can see that the height of the pole is 8 + d tan9°
*March 8, 2016*

**Intermediate Algebra**

If my speed is s, and the current is c, then since distance = speed*time, .76(s+c) = 19 2.11(s-c) = 19 Now just solve for s and c.
*March 8, 2016*

**trig**

well, sin^2(x) = (1-cos2x)/2
*March 8, 2016*

**trig**

sin2x - cotx 2sinx cosx - cosx/sinx (2sin^2x cosx - cosx)/sinx cosx(2sin^2x-1)/sinx -cotx cos2x not sure where you want to go with this
*March 8, 2016*

**math**

Is that f(n) = 4e^(n^3) ? n^3 = ln(f/4) n = ∛ln(f/4) so, f^-1(Q) = ∛ln(Q/4) That is kind of strange, so maybe you can fix it and follow the same logic to find the inverse you want. If you get stuck, show some work...
*March 8, 2016*

**maths**

304 314 324 334 354 364 374 384 384 394 400 401 402 403 405 ...
*March 8, 2016*

**algebra**

Factor out the -2 everywhere. What do you see?
*March 8, 2016*

**math please help**

the slope of the line between the two points is (-3+1)/(2+2) = -1/2 So, its perpendicular has slope 2
*March 8, 2016*

**Mathematics**

y' = 3x^(1/2) - 6 y = 2x^(3/2) - 6x + C y(9) = 2, so 2*27 - 6*9 + C = 2 C = 2 y = 2x^(3/2) - 6x + 2
*March 8, 2016*

**math**

the area is height * width: 47sin60° * 47cos60°
*March 8, 2016*

**MATH, GEOMETRY**

ABCD can be drawn with a right angle at A. Then, if you drop an altitude from CD to AB, it will divide AB into two equal parts of length 8. Now on the right side you have a right triangle, with base=8 and hypotenuse=17. Now you can figure the height h, and so the area is h * (...
*March 8, 2016*

**maths**

2/3 * 30 = ?
*March 8, 2016*

**Maths**

If the circles are arranged in a rectangular grid, only 8 circles will fit across and down. So, what is 8*8 ?
*March 8, 2016*

**Math**

do it just as with the factory inspector
*March 8, 2016*

**maths**

r = 6400 + 700 = 7100km C = 2πr = ... No idea what "standard form" is.
*March 8, 2016*

**science**

change is final minus initial: -80 - 50 = -130 km/hr
*March 8, 2016*

**Math**

30/2 * 8
*March 8, 2016*

**maths**

r/h = 2/3 so h = 3r/2 v = πr^2h = 3π/2 r^3 = 1617 r = 7 so, h = 21/2 Now just find the area a = 2πr(r+h)
*March 8, 2016*

**Trig**

draw your angles in standard position. Recall that sin = y/r cos = x/r tan = y/x That means that: sin u = -√5/6 cos u = -1/6 tan u = √5/1 sin v = √22/5 cos v = √3/5 tan v = √(22/3) I may have misinterpreted the radicals if you were careless with ...
*March 8, 2016*

**physics**

if the speed of sound is x m/s, then if the well's depth is d, 4.9(10-d/x)^2 + d/x = 10 now look up x and solve for d
*March 8, 2016*

**arithmetic**

a+12d = 27 a+6d = 3(a+d) Now you can find a and d, and then get S10 = 10/2 (2a+9d)
*March 8, 2016*

**math**

these are just difference-of-squares exercises. recall that (a-b)(a+b) = a^2-b^2 So, #1: (2x^2)^2 - 4^2 = 4x^4 - 16 now try the others.
*March 8, 2016*

**matthh**

f = (1+8x)/(8-5x) swap variables and you have x = (1+8f)/(8-5f) x(8-5f) = 1+8f 8x - 5xf = 1 + 8f -5xf - 8f = 1 - 8x -(5x+8)f = (1-8x) f = (8x-1)/(5x+8)
*March 8, 2016*

**Math**

Yes, I believe that is what I said in my first sentence.
*March 8, 2016*

**Math**

yes, the limit is always ∞.The limit is Zero when the greater power is in the bottom. This is because when x gets really huge, on;y the highest power counts. You can throw all the lower degree stuff away. So, 3x^3-7x+3 ------------ -> 3x^3/x = 3x^2 -> ∞ x+4 ...
*March 8, 2016*

**Algebra 2**

How about just using the formula for Sn of a geometric sequence? 3(4^8-1)/(4-1) = 4^8-1 = 65535
*March 7, 2016*

**Calculus - Rates of Change**

You were ok to here: V= 4/48 π h^3 V = π/12 h^3 But that means dV/dt = π/12 * 3h^2 dh/dt = π/4 h^2 dh/dt Now plug in dV/dt=2, h=3, and you get π/12 * 9 dh/dt = 2 dh/dt = 8/3π ft/min
*March 7, 2016*

**General**

why beans are not the same size as the one planted
*March 7, 2016*

**Science**

Warm air masses usually form in tropical or subtropical regions and are called tropical air masses. Moist air masses form over oceans and are referred to as maritime air masses. Dry air masses that form over land surfaces are called continental air masses http://wxguys.ssec....
*March 7, 2016*

**math**

x/2 = 2x-6
*March 7, 2016*

**Math**

4.5 * (30/2.5 - 20/2) = 9.0 miles
*March 7, 2016*

**Math**

I assume you know what supplementary means. Thus, 3x+10 + 10x-12 = 180 Find x, and then use that value to determine the angles.
*March 7, 2016*

**analytic geometry**

see your previous post. Was something unclear? If so, show how far you got.
*March 7, 2016*

**Math**

-23a + 4 > -8 4 > 23a-8 12 > 23a 12/23 > a
*March 7, 2016*

**Math**

false 93+12 ≠ 180 adding a number greater than 90 and one less than 90 will not always produce a sum of 180.
*March 7, 2016*

**Math**

see previous post. And geez, have a little patience...
*March 7, 2016*

**Math**

(8.5-1.5)*(11-1.5)
*March 7, 2016*

**math**

7.5, if it's a 1-ft^3 pool.
*March 7, 2016*

**electrical electronics engineering**

google is your friend. Read some articles, some of which will surely be a general description of the system.
*March 7, 2016*

**Trigonometry**

You cannot work this: sin(sin+1) = 3/4 if sin=3/4, sin+1 = 7/4 This is why we always set things to zero. If a product is zero, one of the factors nust be zero. sin^2+sin = 3/4 4sin^2+4sin-3=0 (2sin-1)(2sin+3) = 0 sin = 1/2 or sin = -3/2 only sin = 1/2 is allowed, so θ...
*March 7, 2016*

**English**

Life is like a simile...
*March 7, 2016*

**AP Calculus AB**

using shells, v = ∫[1,4] 2πrh dx where r = x and h = y-1 = x^2-1 v = ∫[1,4] 2π(x)(x^2-1) dx = 225π/2 Hmmm. The area I'm rotating is the shaded triangular region shown at http://www.wolframalpha.com/input/?i=plot+y%3C%3Dx^2,+16%3E%3Dy%3E%3D1,+0%3C...
*March 7, 2016*

**Math**

I guess. Do you not know how to multiply? Have you no calculator? A = 22*7/2 = 77 If this is a real problem, you have much work ahead of you.
*March 7, 2016*

**Math**

by "inside the triangle" I assume you mean the altitude. Recall that the area of a triangle with base b and height h is A = bh/2
*March 7, 2016*

**quadratic equations**

see related questions below. polynomials with real coefficients cannot have equal complex roots.
*March 7, 2016*

**Geometry**

No idea, since I have no diagram, nor any description. But, 53+37=90
*March 7, 2016*

**Algebra**

phil = 2*james peter = phil-3, so peter = 2*james - 3 phil+james+peter = 32 2j + j + 2j-3 = 32 5j = 30 j=6 ...
*March 7, 2016*

**Geometry(stumped)**

1st step is given 2nd step is to subtract 8 from both sides 3rd step is to multiply both sides by 5 So, it looks like B to me
*March 7, 2016*

**geometry**

arcAD:arcDB = 1:4 means m<A : m<B = 1:4 Since AB is a diameter, m<D = x = 90 that should help.
*March 7, 2016*

**Calculus**

The values given for T,w,k indicate y=(T/w)cosh((w/T)*(x))+k = (500/1.5)cos(1.5/500 x) + 80 But this curve does not pass through (300,150) as explained in the beginning. To get that, we need y = a*cosh(x/a)+80 where y(300)=150 But that has no solution.
*March 7, 2016*

**Math**

Very few sequences can be both arithmetic and geometric: a,a,a,a,... has d=0, r=1 to be arithmetic, the difference between two terms must be constant to be arithmetic, the ratio between two terms must be constant For #1, 14, 19, 24, 29 it is clear that you add 5 to each term ...
*March 7, 2016*

**Math**

apparently 14/28 = 50% of the trout have tags.
*March 7, 2016*

**Math**

just divide each term by 4xy: y/2 + 4x - 5 + 2/(xy)
*March 7, 2016*

**Trig sum please help**

enter your matrix of coefficients here and watch the details unfold: http://www.gregthatcher.com/Mathematics/GaussJordan.aspx
*March 7, 2016*

**Math**

cross-multiplying is just a shortcut. Using the normal method of clearing fractions, the steps are x/y = a/b x = ay/b bx = ay bx/a = y or, using the shortcut of multiplying everything by by, you have byx/y = aby/b bx = ay bx/a = y
*March 7, 2016*

**Evaluate sum please help**

surely (2k-1)/(2k-1) = 1 So, the sum is 6 ∑ (-1)^k = (-1)^3 + (-1)^4 + (-1)^5 + (-1)^6 = -1+1-1+1 = 0 3
*March 7, 2016*

**trigonometry**

As usual, draw a diagram. To find the distance z, it's a simple law of cosines problem. z^2 = 92^2 + 50^2 - 2*92*cos117° z = 123.048 Getting the bearing is a bit more work. You have to use x- and y-components of the vectors so you can add them up. Starting at (0,0), ...
*March 7, 2016*

**math**

.25" : 3' = 1":12' so, 2"x3" = 24'x36' =
*March 7, 2016*

**analytic geometry**

draw a diagram. If we put the vertex of the parabola at (0,5) then we have y = ax^2 + 5 y(150) = 60 now you can find a, and then work on y(0), y(50), ... y(150)
*March 7, 2016*

**Calculus: Implicit Derivatives**

No implicit derivatives here -- just the chain rule and lots of tedious algebra... df/dx = df/dg * dg/dx = (4g^3 - g^2)(2x) = (4(x^2-7)^3 - 2(x^2-7))(2x) = 8x^7 - 168x^5 + 1172x^3 - 2716x or, going directly, f(g) = g^4-g^2 = (x^2-7)^4 - (x^2-7)^2 or, x^8 - 28x^6 + 293x^4 - ...
*March 7, 2016*

**Math help please**

Just substitute in values for n: Sn: 2 is a factor of n^2+7n S1: 2 is a factor or 1^2+7*1 S2: 2 is a factor of 2^2+7*2 S3: 2 is a factor of 3^2+7*3 Now just show that each is true.
*March 7, 2016*

**Math - geez - give it a rest already!**

!!!!!!!!!!!!
*March 7, 2016*

**geometric progression**

well, 48 = 3*r^2 or, consider that the geometric mean of 3 and 48 is √(3*48)
*March 7, 2016*

**maths**

d^2 = 6^2 + (13-5)^2
*March 7, 2016*

**math**

v = (48-2*8)(36-2*8)(8) lsa = 2(48-2*8)(8) + 2(36-2*8)(8)
*March 7, 2016*

**Algebra**

Use what you know about parabolas: (a) h(0) (b,c) max height at the vertex, where t = 8/32 (d) solve for t when h(t) = 0
*March 7, 2016*

**Math**

the lion can run 10 mi/hr faster, or 14.67 ft/s so, it will take 1000/14.67 = 68.18 seconds to make up the distance
*March 7, 2016*

**math**

Not sure what all that introductory stuff is, but if y = secx + tanx dy/dx = secx tanx + sec^2x = secx(tanx+secx)
*March 6, 2016*