Friday
April 29, 2016

Posts by steve

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

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