# Posts by Steve

Total # Posts: 49,612

**Algebra**

note that each term has an x. So, factor it out: x(x+6)

*March 26, 2017*

**math**

2x^2-2x 2x^2-15

*March 26, 2017*

**math**

try adding: 2/7 + 1/3 = 13/21 so, 13/21 - 1/3 = 2/7

*March 26, 2017*

**maths**

1/4 = 16r^6 r = 1/2 16,8,4,2,1,1/2,1/4

*March 26, 2017*

**Geometry**

they are similar

*March 26, 2017*

**math**

a = 4?r^2 da/dt = 8?r dr/dt v = 4/3 ?r^3 = ar/3 dv/dt = 1/3 (r da/dt + a dr/dt) Now just plug in your numbers

*March 26, 2017*

**MATHS**

ever heard of math notation? (sin^4x-cos^4x)/(1-sin^2x) = (sin^2x+cos^2x)(sin^2x-cos^2x)/cos^2x = tan^2x-1

*March 26, 2017*

**Maths**

google is faster. For any pyramid, v = 1/3 Bh where B is the area of the base.

*March 26, 2017*

**Maths**

v = 1/3 Bh, so 100 = 1/3 B * 12 Now solve for B, the area of the square base, and then the side is easy

*March 26, 2017*

**calculus**

assuming you want to integrate, let u=ln(3+x) dv = x dx du = 1/(3+x) dx v = x^2/2 ?u dv = uv - ?v du ?x ln(3+x) dx = x^2/2 ln(3+x) - 1/2 ?x^2/(3+x) dx Now just divide, and you will have easy stuff left.

*March 26, 2017*

**calculus**

let u = (lnx)^2 dv = x^-3 dx du = 2lnx/x dx v = -1/2 x^-2 ?u dv = uv - ?v du ?(lnx)^2/x^3 dx = -(lnx)^2/(2x^2) - ?(-lnx)/(x^3) dx Now repeat with u=lnx and you will be left with just a power of x to integrate.

*March 26, 2017*

**Precalculus**

since complex roots occur in conjugate pairs, (x-3)^2 (x-(5+i)) (x-(5-i))

*March 26, 2017*

**Precalculus**

y = (x-2)^2 (x+4)^3 now just expand that.

*March 26, 2017*

**Math**

Let's make things easy by ending up with 21L of the 1:20 solution. That will contain 1L of pure solution. (2/7)x + 0(21-x) = (1/21)(21) x=7/2 So, mix 3.5L of the 2:5 mixture with 17.5L of water

*March 25, 2017*

**physics homework**

depends on the spring constant. asking twice won't help ...

*March 25, 2017*

**Algebra**

1200 * e^(.05*6) = 1619.83 too bad you didn't include your work ...

*March 25, 2017*

**Math**

2^2(7+2^2)+0*1 71-(20+7) There are lots of ways

*March 25, 2017*

**Mathematics**

If (x-1) is supposed to be the altitude, then (x+6 + 3x-4)/2 * (x-1) = 119 x = 8

*March 25, 2017*

**Maths**

Huh? LCM(140,n) has to be at least 140...

*March 25, 2017*

**Maths**

you are correct. I misread the problem. Can you see where?

*March 25, 2017*

**Maths**

(2x+2x+2x)-(10+19+29)+x = 90 Hmmm. I suspect a typo.

*March 25, 2017*

**Chemistry**

see related questions below

*March 25, 2017*

**Science**

(30m/s)/(60s) = 0.5 m/s^2

*March 25, 2017*

**physics**

The resistance of the parallel component is 30R/(R+30) If R' is the equivalent resistance of the circuit, R' = 1/(1/30 + 1/R) + 6 = 36(R+5)/(R+30) The current through the 6? resistor is 120/R' = (10R+300)/(3R+15) The voltage drop across R is [30R/(R+30)]/[36(R+5)/(...

*March 25, 2017*

**Math**

T13/T6 = ar^12/ar^5 = r^7 (3/16)/24 = 1/128 = (1/2)^7 so, ...

*March 25, 2017*

**maths**

506 base 6 does not exist, since base 6 numbers consist only of the digits 0-5.

*March 25, 2017*

**Math**

use the law of sines to show that the base is divided into equal lengths. Then that will imply that the angles at the base of the altitude are also equal, so they are both 90 degrees.

*March 25, 2017*

**math**

50 * (1788/3725)

*March 25, 2017*

**algebra**

just solve the equation x^2 + (1/2 x + 11)^2 = (2x+1)^2 x = 8

*March 25, 2017*

**college algebra**

C(x) is just a parabola. Its minimum value is at the vertex, where x = -b/2a = 7

*March 24, 2017*

**math**

90 years is 3 half-lives. That means that 1/8 of the original amount remains. So, the 1 mg that has decayed represents 7/8 of the original amount. So, starting out at 8/7 g, 1/7 g = 14.27mg remains. ---------------------------------- after 4 half-lives, 1/16 of the original ...

*March 24, 2017*

**college algebra**

Sorry, that -3072 means its initial height (at t=0) is 3072 feet below ground.

*March 24, 2017*

**Math**

since |y| > y, y < 0, so |y| = -y x>|y|, so x+y>0 ==> |x+y| = x+y |x+y|-|x|+|y| = x+y-x-y = 0

*March 24, 2017*

**Math**

4^x = 6 2^x = ?4^x = ?6 8^x = (2*4)^x = 2^x * 4^x = 6?6 or, 8^x = (4^(3/2))^x = (4^x)^(3/2) = 6^(3/2) = 6?6

*March 24, 2017*

**Math**

(A+B)/2 = A + B/10 A/2 + B/2 = A + B/10 A/2 = 2/5 B A = 4/5 B A.B = 4.5

*March 24, 2017*

**Calculus**

2?r^2 + 2?rh = 20 so, h = 10/?r - r the volume is v = ?r^2h = ?r^2(10/?r - r) = 10r-?r^3 so, find r when dv/dr=0

*March 24, 2017*

**Math**

If the walk has width w, then since the parkland occupies 80% of the area, (30-2w)(5-2w) = 0.80*30*5 w = 0.4396m

*March 24, 2017*

**Calculus**

h+4s = 14 v = hs^2 = (14-4s)s^2 so find s when dv/ds = 0

*March 24, 2017*

**Physics**

since V is constant, and PV=kT, P/T = k/V is constant. So, you want P such that P/(273+25) = 7/(273+15)

*March 24, 2017*

**math**

because 1/c = c^(-1)

*March 24, 2017*

**Math**

check your prior post in the related questions below ...

*March 24, 2017*

**Calculus please help!**

consider f'(1) where f(x) = ?x where you should have written the limit as (?(1+h) - ?1)/h

*March 24, 2017*

**Pre calculus**

p(x) = (x-11i)(x+11i) = x^2 - (11i)^2 = x^2+121

*March 24, 2017*

**Physics**

distance = speed * time so, time = distance/speed

*March 24, 2017*

**Math(PLEASE HELP ME ASAP)**

22.50 * 1.15 = 25.875

*March 24, 2017*

**Math(PLEASE HELP ME ASAP)**

well, how did you figure it out?

*March 24, 2017*

**Math**

well, the base has area 132/11 = 12 so ...

*March 24, 2017*

**Calculus**

(a) c = 13(4x+y+4x+y) + 5(3y) = 112x+41y (c) xy=9, so y=9/x, and c(x) = 112x + 369/x now find x where dc/dx = 0

*March 24, 2017*

**Math**

huh? Just solve (75+x)(225-5x) = 16000 x = 5 so, ...

*March 24, 2017*

**Precalculus**

a) ok b) The average cost is the cost per unit, or c?(x) = c(x)/x So, c?(x) = 0.02x + 0.5 + 40/x The marginal average cost is thus c?'(x) = 0.02 - 40/x^2

*March 24, 2017*

**Algebra - rats**

I see other typos. The final answer is correct, but let me just do it right: Since the vertex and focus both lie on the line x = -2, the axis of symmetry is vertical, meaning the equation is (x-h)^2 = 4p(y-k) Since the focus above the vertex, p is positive. You know that the ...

*March 24, 2017*

**Algebra - typo**

As you noticed, the axis is vertical, on he line x = -2

*March 24, 2017*

**Algebra**

Since the vertex and focus both lie on the line x = =2, the axis of symmetry is horizontal, meaning the equation is (x-h)^2 = 4p(y-k) Since the focus above the vertex, p is positive. You know that the parabola x^2 = 4py has the vertex at a distance p from the focus. Here, that...

*March 24, 2017*

**Math, Algebra**

If you drop an altitude to the center of the base, then looking from the side you have a right triangle with legs 4 and 22. So, the hypotenuse of the triangle (the slant height of the pyramid, and the altitude of each triangular face) is h = ?(4^2+22^2) = ?500 = 10?5 That ...

*March 24, 2017*

**MAth help connexus**

c - review the section on functions, esp. the vertical line test.

*March 24, 2017*

**math - trigonometry**

one walks on a heading, not a bearing. a) Note that angle Q is 90 degrees, so you have a right triangle. Easy... b) This is the correct use of "bearing." If the bearing is x, then tan(x+25) = 18.7/11.4 A diagram will show you why.

*March 24, 2017*

**Math Measurment unit test**

1. A = bh 2. A = bh/2, so looks good.

*March 24, 2017*

**math**

2/s = 1/4 + 1/5

*March 24, 2017*

**math**

well, the volume of water flowing in every second is 1.2cm * 350cm/s = 420 cm^3/s Now divide the volume of the tank by the inflow rate to get the time (in seconds)

*March 24, 2017*

**calculus**

The 13 is just a scale factor, and has no bearing. You know that ? ? 1/10^n = 0.11111111 = 1/9 n=1

*March 24, 2017*

**Maths**

If the 5th is 4 times the 3rd, then r=2 a+ar = -4 a+2a = -4 a = -4/3 now take it from there.

*March 23, 2017*

**math**

Let the man run to point P, which is x meters upstream from the line AB. He swims across, being swept y meters downstream, and then runs to B. We know that he is in the water for d/(v/3) = 3d/v seconds, so y = 3d/v * v = 3d. His path is thus ?(d^2+x^2) meters on land, d meters...

*March 23, 2017*

**math**

again c? aa

*March 23, 2017*

**math**

before: 00AF

*March 23, 2017*

**math**

before: AFc after: cAF

*March 23, 2017*

**math**

c-bar ̅

*March 23, 2017*

**Math**

well, the last digit is 5 start there.

*March 23, 2017*

**Physical science**

2Na + 2H2O = 2NaOH + H2 now just multiply everything by 3/2

*March 23, 2017*

**Math**

y = x-12

*March 23, 2017*

**Math**

write them as 4x-6y = -48 x+6y = 18 add them together and you get 5x = -30 ...

*March 23, 2017*

**chem**

assuming a constant temperature, PV = kT is constant. So, you want P such that P*2.94 = 0.988*3.35

*March 23, 2017*

**Math**

y = 1+2x 3x+(1+2x) = 11 ...

*March 23, 2017*

**chem**

assuming a constant temperature, PV = kT is constant. So, with 5/4 the pressure, you get 4/5 the volume

*March 23, 2017*

**Math**

square both sides write cos^2 = 1-sin^2 Then you have a quadratic in sinx

*March 23, 2017*

**physic**

how long does it take to fall 160m? The horizontal speed does not affect that. 4.9t^2 = 160 Now, the horizontal speed does not change, so the body travels 20t meters

*March 23, 2017*

**Math1**

You want t years, where 2100(0.95)^t = 600 0.95^t = 2/7 t = log(2/7)/log(0.95) = 24.42

*March 23, 2017*

**Pre-cac**

well, even without completing the square, you know the vertex is at x = -b/2a = 3/2a So, a(3/(2a))^2 - 3(3/(2a)) + 5 = 15 5 - 9/(4a) = 15 a = -9/40 But, in the spirit of completing the square, ax^2-3x+5 = a(x^2 - 3/a) + 5 = a(x^2 - 3/a + (3/2a)^2) + 5 - a(3/2a)^2 = a(x - 3/2a...

*March 23, 2017*

**Maths**

4000*1.015^2 = 4120.90

*March 23, 2017*

**Math**

a. correct b. The volume with the cuts made and the sides folded up is v = (12-2x)(18-2x)x = 4x^3-60x^2+216x If you have calculus, then dv/dx = 12(x^2-10x+18) dv/dx=0 when x=5-?7 ? 2.35 If no calculus, then a graphical or numeric method is needed.

*March 23, 2017*

**Math**

(x,y)-> (x-4,y+1) is correct. But you still botched it: (-3,1) -> (-3-4,1+1) = (-7,2) + means ADD: 1+1 = 2, not 0! same for subtracting: -3-4 = -7 -3+4 = 1 -1 is just plain bogus, man.

*March 23, 2017*

**Math**

left 4 means subtract. as you said, up 1 means add. But even if your translation were correct, you did not do the math right 1+1 ? -2 Try again. You're getting the +'s and -'s mixed up some.

*March 23, 2017*

**Math**

naturally, we can see no graphs here. What are your choices for the others?

*March 23, 2017*

**Math**

(a) trés simples, non? (b) 2x cosy - x^2 siny y' - cosy y' = 0 y' = (2x cosy)/(cosy + x^2 siny) So, at (0,?), y'=0 (c) so, the tangent is a horizontal line, and the normal is a vertical line through (0,?).

*March 23, 2017*

**Pre-calculus**

I will assume a typo, and work with x^2+10x+4y+9 = 0 That may not be what you had in mind, but you can follow the method using your corrected equation. x^2+10x+4y+9 = 0 4y = -x^2-10x-9 y = -1/4 x^2 - 5/2 x - 9/4

*March 23, 2017*

**Math 120**

6+2 + 2 (conversion+safety) 6+1 + 3 6+2+2 (two safeties) 3+3+2+2 2+2+2+2+2

*March 23, 2017*

**math**

the nice thing about Ø is that Ø-1 = 1/Ø

*March 23, 2017*

**math**

sinx = cos^2x sinx = 1-sin^2x sin^2x + sinx - 1 = 0 now solve for sinx, and pick the positive solution.

*March 23, 2017*

**Calculus - Newton's Method**

well, f'(x) = 1-sinx So plug that into Newton's method. Here is a nice web site: http://keisan.casio.com/exec/system/1244946907

*March 23, 2017*

**calculus**

you will need to use integration by parts, twice. 1st step: u = t^2 dv=sin(2t) dt du = 2t dt v = -1/2 cos(2t) That makes the first integration by parts: ?u dv = uv - ?v du ?t^2 sin(2t) dt = -1/2 t^2 cos(2t) + ?t cos(2t) dt Then repeat, letting u = t dv = cos(2t) dt You should ...

*March 23, 2017*

**Calculus**

I suspect a typo, since what you have written is just f(x) = x/(x+x^2) = 1/(1+x) f' = -1/(1+x)^2 f" = 2/(1+x)^3 Anyway, fix that, find f", and recall that f"=0 means an inflection point f" > 0 means concave up f" < 0 means concave down

*March 23, 2017*

**calculus**

use integration by parts. That is just the product rule in reverse. d(uv) = u dv + v du u dv = d(uv) - v du ?u dv = ?d(uv) - ?v du ?u dv = uv - ?v du So, here we just let u = (lnx)^2 dv = dx du = 2lnx * 1/x dx = (2lnx)/x v = x ?(lnx)^2 dx = x(lnx)^2 - ?2lnx dx Now repeat, this...

*March 23, 2017*

**math**

x >= 15000/12 = 1250 So, consider how long a ride might take, and how long the park is open each day.

*March 23, 2017*

**math**

5 divides evenly any multiple of 5. Not sure what you mean by "5 divide into equaly" [sic]

*March 23, 2017*

**Help please I am lost, algebra**

if g(14) = -6, then that means you have the point (14,-6) on the graph. Using the point-slope form, then, you get y+6 = -5/4 (x-14) Now massage that to the slope-intercept form: y+6 = -5/14 x + 35/2 y = -5/14 x + 23/2

*March 23, 2017*

**Math**

The first model is linear because the changes are constant. In fact, y = x/2 - 1 For the second, check the differences: 1st: 5.1, 20.4, 81.6, 326.4 2nd: 15.3, 61.2, 244.8 If t were quadratic, the 2nd differences would be constant. Since they are also growing rapidly, you ...

*March 23, 2017*

**Functions, please help**

2700x+21000 = 83400 just solve for x 2010 is 7 years after 2003, so just plug in x=7 for P(x)

*March 23, 2017*

**Physics**

Let the man run to point P, which is x meters upstream from the line AB. He swims across, being swept y meters downstream, and then runs to B. We know that he is in the water for d/(v/3) = 3d/v seconds, so y = 3d/v * v = 3d. His path is thus ?(d^2+x^2) meters on land, d meters...

*March 23, 2017*