# Posts by Steve

Total # Posts: 50,482

**Math**

well you multiply by -4, so B looks good.

**Math**

1) 30cm * ?48m * 12m = 24.94 m^3 ... 3) ?/4 * 3^2 * h = 24.94 Now the rest should not be too hard. Come back if you get stuck.

**Linear algebra**

This is just a standard rotation matrix, explained here: https://en.wikipedia.org/wiki/Rotation_matrix

**Calc AB**

V(t) = 100 + (5t+4) - t^2/2 so you are correct there. V'(t) = 5-t So, you are correct that V is a max at t=5 The average value of a function is (?[a,b] f(t) dt)/(b-a) So, that means that #3 is ?[0,5] (-0.5t^2+5t+104) dt = 337/3 So, you want to find when (-t^2/2 + 5t + 104...

**math**

in 1969: 32000 / 1.0583^45 = ? in 2059: 32000 * 1.0583^45 = ?

**maths**

well, r^3 = 96/12 = 8, so r=2 take it from there.

**Math -- Calculus**

If the printed area has dimensions x and y, then xy=A, so y=A/x The actual page has dimensions x+L+R and y+T+B To minimize the page area, then you want to minimize f(x,y) = (x+L+R)(y+T+B) f(x) = (x+L+R)(A/x + T+B) = (T+B)x + A + A(L+R)/x + (L+R)(T+B) df/dx = (T+B) - A(L+R)/x^2...

**Calculus**

Try changing the equations in your earlier post to reflect the new parameters. How far do you get?

**Calculus - Optomization Problem**

see related questions below. In particular, http://www.jiskha.com/display.cgi?id=1318801288

**Math**

review the associative property of addition.

**College Algebra**

swap variables x = 4-y^2 y = ±?(4-x) But you need to pick the branch where 4-x >= 0. take a look at the graph and I'm sure you can answer the questions. http://www.wolframalpha.com/input/?i=%E2%88%9A(4-x)

**Calculus**

As always, draw a diagram. It is clear that if the length of the rope is z when the boat is x ft from the dock, z^2 = x^2+36 z dz/dt = x dx/dt Figure x when z=10, then just plug in your numbers and solve for dx/dt.

**Calculus**

I don't know how the liquid can drain and leave the substance behind, if it's dissolved. Maybe it's just in suspension, and the liquid drains through a filter. Anyway, the volume of water at time t hours is v = 60-4t The concentration is c(t) g/L = 100/v(t) = 100/(...

**Calculus**

y = 2?x - 4 since x and y are both functions of t, think chain rule: dy/dt = 1/?x dx/dt Now just plug in your numbers and you have dy/dt = 1/2 * 9

**Maths**

see your other posting -- this is just the same idea.

**Maths**

PQ is 4 units from AD and 6 units from AB. So, The slant height of ?ABP is ?(15^2-6^2) The slant height of ?ADP is ?(15^2-4^2) Now you can easily figure each area, and then the cost.

**Maths**

I have no idea which vertices are VEF, but just draw a diagram and note that the distance from the center pole to the base of the triangle is 1/2 the side length adjacent to the base of the triangular face. Then you can get the (slant) height of the triangle using the ...

**Math!**

see your other post in the related questions below.

**physics - eh?**

Try again, but not in gibberish

**angular velocity/ physics**

500 rotations is 1000? radians, so ? = 1000?rad/10s = 100? rad/s

**Calculus help**

Hmmm. Figured it out in two minutes! Less time than it took you to post the problem, I'd say...

**math**

b/(b+g) = 3/4 g = b-24 b/(2b-24) = 3/4 4b = 6b-72 b = 36 so, g=12 making 48 pupils in all

**grammar**

Extra credit: what's the difference between shall and will?

**Calculus (related rates)**

If the base of the ladder is x feet from the wall, and the ladder reaches up y feet, then we have x^2 + y^2 = 13^2 taking derivatives wrt t, x dx/dt + y dy/dt = 0 Now just plug in your numbers and solve for dy/dt (note that at the moment in question, you conveniently have a 5-...

**Calculus (related rates)**

do this like your earlier one, using the chain rule.

**Calculus (related rates)**

just use the chain rule. Since x and y are both functions of t, dy/dt = (4x+2) dx/dt Now just plug in your numbers

**Calculus**

just crank it out. The acceleration is a(t) = 0.0044875t^2 - 0.17879t + 18.86 a(t) has a max/min when da/dt = 0 da/dt = 0.008975t - 0.17879 da/dt=0 at a=19.9209 a(10.9209) = 17.0792 Since a(t) is a parabola, there is no maximum value, but in the domain [0,50.2], the maximum ...

**Math**

Draw a diagram. If the ladder's length is z, and the base of the ladder is x feet from the fence, then by similar triangles, you can see that z/(x+3) = ?(x^2+9)/x z = (x+3)?(x^2+9)/x dz/dx = (x^3-27) / (x^2 ?(x^2+9)) dz/dx=0 when x=3 z(3) = 6?18/3 = 6?2

**Math Check!**

2975*1.04^2.5 = 3281.48 But, technically, since the interest is not compounded till the end of the year, you might get 2975*1.04^2 = 3217.76 Since that is not listed, I'd go with B So, how did you get D? That's over double the initial amount. Not likely!

**Algebra**

.03b + .10(20000-b) = .08*20000

**maths**

a = 4b .17a + .10b = 234 so, .78b = 234 b = 300

**Math (higher level) 2nd year**

(3x-2)(2x-4) = 14 6x^2-16x-6 = 0 2(x-3)(2x+1) = 0 x = 3 So the bed is 7x2 But you could have guessed that at first, since 2 and 7 are the only factors of 14...

**real estate**

x * 1.06^2 = 140000

**science**

see related questions below.

**Relative Clauses and Pronouns**

all look ok to me. Of course, the purists would write 5. This is the tiger for which the hunters have been looking. Like the small boy who noticed his father had brought the wrong bedtime story, and said: What did you bring that book I don't want to be read to out of up for?

**Calculus**

think of the volume as a stack of discs of thickness dx, and you have v = ?[0,?] ?r^2 dx where r=y=cos(cos(x)) v = ?[0,?] ?cos^2(cosx) dx This is not an elementary integral, so some numeric method is needed. However, using some symmetry, v = 2?[0,?/2] ?cos^2(cosx) dx and you ...

**Calculus**

Each semicircle resting on the x-y plane has radius x=?(16-y^2). Adding up all the slices, and using symmetry, we have v = 2?[0,4] 1/2 ?r^2 dy = ??[0,4] (16-y^2) dy = 128?/3 bobpursley's solution is much more intuitive and geometric, though, eh?

**Calculus**

Hmmm. Let me take a stab at it. AT (-4,1) we have ln(x^2-15y) = ln(1) = 0 Hmmph. Can't make out a reasonable interpretation that is zero on the right. Anyway, regardless, let's just say that it is ok as it is. Then we have, taking derivatives of both sides, using the ...

**Math**

correct

**math**

Since the axis of symmetry is x=3 and the y-intercept is E, the parabola is f(x) = a(x-3)^2 + E since E is the y-intercept of the parabola, E = -7/2 f(x) = a(x-3)^2 - 7/2 Now you know that (7,0) is on the parabola, so a(7-3)^2 - 7/2 = 0 16a = 7/2 a = 7/32 f(x) = 7/32 (x-3)^2...

**math**

well, ?5 ? 2.236 I assume you can mark that on the number line. . .

**math**

{1,2}?{2,3} = {1,2}?{2,5} I'm sure you can handle the Union one...

**math**

I believe exterior angles are 180 - interior angles. Their sum is 360.

**Algebra**

.06^(1/12) = ?

**algebra**

L(L-3) = 46.75 solve for L and W, then P = 2(L+W)

**Science**

you'll probably get a faster response from google: https://www.google.com/search?q=What+are+the+uses+of+reactivity+series&ie=utf-8&oe=utf-8

**MAATH!!**

correct

**Math**

720 = 36*20 so, count the good ones here and multiply by 20 to estimate the larger amount.

**Science**

KE = 1/2 mv^2 and that's "wrecking" ball, but it does wreak havoc ...

**maths**

Now, use the fact that v(0) = 10 (4t^5/5)-(8t^3/3)-9t+v0 = 10 at t=0 So, v0 = 10, and thus v(t) = (4t^5/5)-(8t^3/3)-9t+10 Now go on to x(t), using x(0) to find the constant of integration.

**Physics**

Adding 20cm^3 of liquid added 20g of mass, so the density is 20g/20cm^3 = 1 g/cm^3

**calculus**

y" = 4 y' = 4x+c y'(1)=10, so 4+c = 10 c=6 y' = 4x+6 No do the same to move on to y.

**Maths**

4/5 the time, so 5/4 the workers: 80 so, another 16 are needed.

**ALGEBRA I**

1st step: write a function for each company. For example, Rider: y = 50 + 0.50x now what?

**Algebra II**

assuming a linear rate of depreciation, the car loses $3900/year. So, after x years, its value is v(x) = 16800 - 3900x

**Math**

Assuming you meant f(x)=-2x*4^(x-1)+3 the domain of all polynomials (-2x) is (-?,?) the domain of all exponentials is (-?,?) so, the domain of f(x) is likewise (-?,?) now work with the ranges in like wise. x -> (x-h) translates right by h y -> (y-k) translates up by k y...

**Algebra**

compare Bh to 1/3 Bh in each case for volume similarly for area

**Math**

just plug your points into x^2/a^2 + y^2/b^2 = 1 then solve for 1/a^2 and 1/b^2

**Math**

The direction numbers for the last two points make the line from t=0..1 x = 2-t y = 0-t z = -1+4t So, backing up to z=3, -1+4t = -3 t = -1/2 a = x(-1/2) = 5/2 b = y(-1/2) = 1/2

**Calculus - Integrating**

The problem is that you did not have du in your integrals. You lacked the extra 2x dx in your integrands. u = x^2+1 du = 2x dx x = ?(u-1) So you have ?x/?(x^2+1) x dx = 1/2 ??(u-1)/u du which isn't really much better Try using a trig substitution: x = tan? x^2+1 = tan^2...

**math**

s = t^3-9t^2+3t+1 v = 3t^2-18t+3 = 3(t^2-6t+1) so, solve for t when v=-24 a = 6t-18 then plug in that t to find v and a. what is your problem with minus signs (-) ? over- and under-score really are ugly! x^2 cosy - siny = 0 Surely you can plug in the point to verify it fits! ...

**MATHEMATICS**

plug your numbers into the formulas found here: https://www.google.com/search?q=cone+area&ie=utf-8&oe=utf-8

**Science**

2Mg + O2 -> 2MgO now convert to moles for amounts needed

**College algebra**

If the half-life is k years, then after t years, (1/2)^(t/k) remains. Thus, to find k, solve (1/2)^(400/k) = 0.7 600 = 3/2 * 400, or 1.5 half-lives. So, the amount remaining after 600 megayears is (1/2)^(3/2 * 400/k) = (1/2)^(400/k)^(3/2) = 0.7^(3/2) = ?

**English**

the literary device of foreshadowing is used in which of the following excerpts? They're spoiled and we're spoiled Those screams -- they sound familiar I have a feeling it'll be Africa again before then They're not old enough to do that alone, I explained My ...

**English**

thank you

**English**

my second choice was number 2

**English**

Which of the following is a way that imagery can be used? to present facts during debates to inspire audiences during speeches to entertain readers with a play on words to impress readers with facts and evidence My answer is the third one

**English**

Then it would have to be subjective

**English**

when doing research writing it is important to avoid being? timely, detailed, objectives, subjective My answer is detailed

**Mathematics for social science**

20P3 10C4

**English**

I agree with your comments. thank you

**English**

Absurdism is the attempt to show the ________ of the human condition. silliness seriousness uniqueness hopelessness my answer is the last one

**English**

thank you

**English**

Scientists report (1) that creatures living in the deep sea are in danger of starving to death. The underlined part of sentence 1 is what kind of clause? adverbial clause adjectival clause noun clause Independent clause My answer is independent because if you remove the word ...

**math**

75% = 3/4 He gave 42 to Joe

**math**

I'm assuming your asking how many did Keith get? 56*3/4=42 Leon gave to Joe 42*2/7=12 Joe gave to Keith 3/4= 75% 2/7=28.6%

**Calculus**

The weight of oil in the tank is w = (20*25? m^3) * (820 kg/m^3) * 9.8 = 4018000?N The center of gravity of the oil is 20m from the top of the tank, so the work required to empty the oil is 4018000? * 20 = 80360000? J Or, using calculus, the weight of oil in a thin layer of ...

**Physics**

Scroll down some here, and all is explained. http://www.insula.com.au/physics/1279/L14.html

**Math Functions Functions**

to shift right by h, replace x with (x-h) to shift up by k, replace y with (y-k) Thus, y-3 = (x-2)^2 shifts y=x^2 right 2 and up 3. Reflecting across an axis changes the sign of the other variable. Thus -y=x^2 reflects y=x^2 across the x-axis. Now see what you can do.

**math- factoring**

If two polynomials are identical, all the coefficients must match. So, a = 2 b = -13 c = 21

**Math**

(5?3,5)+(0,-4) = (5?3,1)

**Math**

in standard form, you have x^2+4x - 4(y^2-6y) = 28 x^2+4x+4 - 4(y^2-6y+9) = 28+4-4*9 (x+2)^2 - 4(y-3)^2 = -4 (y-3)^2 - (x+2)^2/4 = 1 Now use that with your standard properties of hyperbolas. check with this: http://www.wolframalpha.com/input/?i=hyperbola+(y-3)%5E2+-+(x%2B2)%...

**Math**

|p| = ?(42^2+35^2) = 7?(6^2+5^2) tan? = 35/42 = 5/6

**Math**

.075x + .12(5000-x) = 819

**Physics**

(10cos37,-10sin37)+(-14,0) = (-6,-6)

**Advanced Functions**

look at the differences. 1st: -0.2, -0.6, -1.0, -1.2, ... 2nd: -0.4, -0.4, -0.4, ... so, look for a linear relationship between y and x^2: y = 3-5x^2 fits pretty well, at least at first

**Math**

cos(2x) = 1 - 2sin^2(x) now just use your numbers.

**Math**

A. 32.65+(38.4-25) = ? B. 32.65+(x-25) = 50.15

**numerical methods in finance**

Just plug in your formula. If you have trouble with that, youtube has several videos showing examples.

**math**

small = 47/22 - 1/2 large = small + 40/11 small = 36/22 large = 116/22

**Geometry**

it is easy to show that ?NOD ? ?MOB check out vertical angles and recall that the diagonals bisect each other.

**Math**

y = 550 * 0.948^t

**Math**

recall that the sum of two adjacent angles is 180, so ...

**Math 120**

(3990-1890)/3990

**Maths**

clearly, P(3k) Q(2k)

**Math**

review the cot(x) function: h cot30 - h cot45 = 1

**Math**

tan? = 9/3 and try proofreading what you type. It's a mess.

**calculus**

what, you can't just plug in the 6 values of t? Even after the explicit example given? No calculus needed here, just basic algebra!

**Maths**

gotta be (d) since the point spread does not change