Saturday

July 26, 2014

July 26, 2014

Total # Posts: 23,965

**Acceleration physics**

#1 Keep track of the units. We want time, which is (m/s) / (m/s^2) SO, divide the change in velocity by the acceleration used: -8.9 m/s divided by -2.7 m/s^2 = 3.30 s #2 ok #3 The velocity change by 80 m/s in the W direction. This change took 5.9 seconds, so assuming constant ...

**math**

since time = distance/speed, If Jake's speed is x, 270/x = 270/(x+15) + 1.5 x = 45 So, it takes Jake 270/45 = 6 hours

**Math 4 grade**

if you have 9 squares and 9 digits, that only leaves on digit for each square. I can't see how to add 3 single-digit numbers to get anything greater than 7+8+9=24. Is there a trick, or something missing here?

**math**

well, obviously, one lap is 1/6 of a mile. That should help...

**Math**

as written, I get x^3 - 8/x^2 + 2x + 4 If you mean 11 + (x^3 - 8) / (x^2 + 2x + 4) - x then that's just 11 + x-2 - x 9 recall the factorization of the difference of cubes.

**Algebra**

well since 15 = 3*5, I guess that pretty well solves the problem, no?

**Algebra 1 Answer Evaluation**

correct. good work.

**Algebra 1 (Step-by-Step)**

this has been answered already. Reiny just stated that since x^2 is always positive, there's no real value of x which can produce -7 when squared. Damon actually wrote the quadratic in standard form, applied the formula and gave the complex solutions. http://www.jiskha.com...

**Algebra**

5(w-10)(w+15-10) = 1250 Now just solve for w. length=w+15.

**math - ouch!**

How did I ever get k=3? My Bad!!

**math**

you know that d = kt, meaning that their ratio d/t is constant. Note that in each case, d/t=3 That means k=3. So, d = 3t

**Algebra 1 (Reiny)**

do you know what the standard form is? Can you apply the quadratic formula? In both these cases, it happens that b=0. Don't be thrown off by that. 0 is just as good a number as any other.

**math**

well, naturally, we have no way of knowing what graphs you have on your paper. Draw your own graph, and see whether it looks like one of your choices. The line naturally, does not stop at -6, though you don't even say whether that is x or y.

**MATH 1 QUESTION PLS HELP ASAP!!!!!**

there's no problem with 15/0, since 3^0 = 1. But that also means that (c) is out because 5*3^n cannot ever be zero. Can't see why you were so surprised at (d), since these sequences usually start with n=1 unless they say otherwise. (b) starts with n=0.

**Algebra**

I assume you mean the vertex is at (3,-8) and the graph passes through (5,-2) The vertex tells us that y = a(x-3)^2 - 8 Now just plug in the point to solve for a: -2 = a(5-3)^2 - 8 4a = 6 a = 3/2 y = 3/2 (x-3)^2 - 8 and the graph shows this at http://www.wolframalpha.com/input...

**Algebra**

since e^x -> 0 for large negative x, the asymptote lies at k=8.2 The k-intercept, where x=0 is very easy, since e^0 = 1. I'll do #3; maybe you can do #4 in like wise: k(-2) = -3.7e^(0.8*2) + 8.2 = -3.7e^1.6 + 8.2

**Algebra**

x(5x-12) / (x+8)(x-3) = 0 We have several points where the graphs crosses the x-axis or has an asymptote. Since there are no double roots in the denominator, the function will change sign at the asymptotes, as well as at the zeros. So, we need to check the sign of the function...

**Math**

reflection takes (x,y)->(x,-y) translation takes (x,y)->(x,y+56) So, g(x) = -f(x)+56 = -4√(2x^2-1)+56 For the other set, note that f^-1(3) = 2, since f(2) = 3 g^-1(4) = 3 So, (g○f)(2) = g(f(2)) = g(3) = 4 By definition, (f○f^-1)(x) = x for any x (fχ...

**pre cal**

I think you can easily get your answer here: http://davidmlane.com/hyperstat/z_table.html

**math**

Well, the spacing makes me interpret this as (3+x)/(7+x) = 3/7 + 3/7 I still suspect a typo on the right side, but now at least we have (3+x)/(7+x) = 6/7 7(3+x) = 6(7+x) 21+7x = 42+6x x = 21

**Pre-algebra**

next step: plug in what you know 70 = 2(17) + 2w Now just solve for w.

**geometry**

2(pi/2*.5 + .5 + 3 + .5 + pi/2*.5) = 8+pi

**geometry - incomplete**

It would help to have the statements ...

**Algebra help please!**

cute way to phrase the question! Let's change the values so they are all between 0 and 360° 591 - 360 = 231 231 = 231 51 = 51 -129 + 360 = 231 Looks like C is the odd man out.

**Math**

V = 1/3 Bh 78.6 cm^3 = 1/3 B(6 cm) B = 39.3 cm^2

**alegbra**

just solve for p in p(1+.055/4)^(4*3) = 990 8y 155d = 8.43 years, so p*e^(.0855*8.43) = 225500

**math**

30*9 = 270 So, add 270-250 the rate the other workers have is just noise.

**geometry - incomplete**

BA + AC = BC 7w-12 + 6w-14 = BC 13w-26 = BC Now you need to know what BC is to find w. I suspect that BC is a multiple of 13, no?

**5th grade math**

to double the volume, double any one (and ONLY one!) of the dimensions. SO, your mission, should you choose to accept it, is to pick the dimension which will produce the most practical shape for the new box.

**ALG**

well, plug in -2x+3 for y: -2x+3 = x^2-x-3 x^2+x-6 = 0 (x+3)(x-2) = 0 Looks like two solutions to me. I'm sure you can figure them out, eh?

**Mahts**

300 = (100+b)2 now divide by 2: 150 = 100+b now subtract 100 50 = b You can always check your answer. For your case, 100 + 300/200 = 100 + 1.5 = 101.5 2x101.5 is not 300 To continue with your proposed solution, correct the distribution of the 2. 300 = (100+b)2 300 = 100(2) + b...

**Consumers Math**

divide the $80 by 6 to see how much each oil change costs with a coupon. So, you want to find out what percentage the discount is of the retail price of $15.95. So, subtract the coupon price from the retail price to get the savings, then divide that by the retail price. And, o...

**physics**

(a) just divide 790N by 1950 nails to get the force in N/nail (b) Now just change the number of nails to total area to get the pressure in N/m^2

**Maths**

She had 3/5 left, SO .6x = 21 x = 35

**science**

As I recall, we have the thermal expansion equation is dL = Lα dT where α for steel is 13.0*10^-6 m/m /°K So, since we want the diameter of the hole to increase by 0.0003 cm, we want the circumference to increase by .0003pi = .0009425 cm = 9.425*10^-6 m So, now w...

**math - PS**

sorry - forgot to eliminate my first line of thought; skip that stuff about |z| and |w|. There's probably a nice complex-number way to do this, but this was my first approach.

**math**

In other words, the two vectors are perpendicular If the two magnitudes are equal, then assuming that |z| >= |w| |z| = √(a^2+b^2) |w| = √(c^2+d^2) z+w = (a+c)+(b+d)i z-w = (a-c)+(b-d)i √((a+c)^2+(b+d)^2) = √((a-c)^2+(b-d)^2) (a+c)^2+(b+d)^2 = (a-c)^2...

**Math - PS**

Well, my most obvious mistake was using 3 as the length, not 300 (cm).

**Math**

when the water has depth y cm, the width of the surface has width 25+(75/50)y cm So, at depth y, the area of the trapezoidal cross-section is 1/2 (25 + (75/50)y)(y) = 3/4 y^2 + 25/2 y cm^2 So, the volume is v = 9/4 y^2 + 75/2 y cm^3 So, we want dy/dt when y=25, and we know tha...

**Math-Exponential Decay**

if the half-life is n days, then the amount remaining after t days can be modeled by 58(1/2)^(t/n) So, to find n, we just have to solve 58(1/2)^(10/n) = 52 (1/2)^(10/n) = 52/58 = 0.8966 10/n = log(52/58)/log(1/2) 10/n = 0.1575 n = 63.5 So, the half-life is about 63.5 days

**math**

I assume the pool is rectangular, with width x and length y. So, if the deck has width w, 2(x+y) = 50 2(x+2w + y+2w) = 74 2(x+y)+2(4w) = 74 50+8w = 74 8w = 24 w = 3

**maths**

to solve algebraically, just solve 3x-6 = x^2-6x+8 x^2-9x+14 = 0 (x-7)(x+2) = 0 The graphical solution is at http://www.wolframalpha.com/input/?i=solve+x^2-6x%2B8+%3D+3x-6

**Math**

thank you

**Math**

Solve the following 2a(a squared+4a)

**algebra**

If you mean h(t) = s - 16t^2 then we need s so that s-16*9 = 0 s = 144 ft

**Algebra**

ummm. The scores. If there are 10 scores, the 80th percentile ends at the 8th score. That is 80% of the scores. Extra credit: what is "context"?

**Algebra**

sort the scores in order. Find the lowest score greater than 80% of them. That is the 80th percentile score.

**math**

(2a) / (2u)(2v) = 2/4 * a/uv = 1/2 a/uv So, #3.

**Math**

The function rule C= 10 n + 26 where n = number of people and c = cost of party. Show a table if 27,39 , & 43 people go. My answer is the following n 27 39 43 c 296 416 456

**Math**

Write a function rule for the following table. x 2 4 6 y 1 0 -1

**Math**

Is y= -3 x squared +x a quadratic function?

**Math**

thank you

**Math**

If you have the following points for X and Y what is the linear function rule? x = 4, 1 y = 2, -4 I think it is 1/2 x but I'm not sure if it is +6 or - 6

**Math**

Now way it can be y=8x+8. adding two even numbers always produces another even, and most of your y values are odd. Also, if a relation is linear, then equal changes in x will produce equal changes in y. Here, we have x changing by 1 between steps, yet y changes by 8,7,9,8 So, ...

**Math**

Using the table below is it a linear function? x -2, -1, 0, 1, 2 y -7, 1, 8, 17, 25 my answer is that it is a linear function rule: x = -1 y = -8,-9,-7, -8 I think the rule is y= 8 X+8

**Math**

It was what I was doing. Thank you

**Math**

Solve for 5 X 3 to the nth,. my answer is 15, 45, 135, 405

**Math**

Is the following sequence a arithmetic,geometric or neither? 1.6, .8, .4, .2 my answer is geometric

**grammer**

Have you seen my sister Karla around here today? Harriet couldn't study for her comma quiz, because she asked to open the door for the neighbor, whom the dog wouldn't leave alone in the backyard.

**algebra**

I assume you mean to let x represent the "second" angle. So, we have x+23 + x + 6x = 180 Now just solve for x. After that, I assume you are supposed to indicate the measure of each of the angles...

**Aths**

throw a tool away from the ship. Conservation of momentum will cause you to drift slowly toward the ship.

**Math**

the surface was 4 pi r^2 = 36pi Now, replace r with (3/2) r and the new surface area is 4pi(3/2 r)^2 = 4pi * 9/4 r^2 = 4pi r^2 (9/4) = 36pi(9/4) = 81pi Or, you could just solve for r and get that r increased from 3 to 9/2, so the area increased from 36pi to 81pi.

**Math**

for each year, just add 4.5 t

**Calc**

y' = -.15y dy/y = -.15 dt lny = -.15t+c y = ce^-.15t with y(0) = 3, c=3 with y(0) = 4, c=4 with c=3, 3e^-.15t = 1 e^-.15t = 1/3 -.15t = ln(1/3) t = ln(1/3)/-.15 t = 7.32 with c=4, t = 9.24 So, the patient gets the 3rd dose after 7.32+9.24 = 16.60 hours.

**Calculus**

Ok. The information for S allows us to determine p, since the distance SF equals the distance from S to the line x = -p. So, 2p+5 = 10 p = 5/2 The equation of the parabola is y^2 = 4(5/2)x = 10x y = √(10x) Now we have to look at T. The slope of the tangent to the curve a...

**math**

If Ann not buy pink, Tom not buy red.

**Algebra**

sort the values, then divide them into four equal parts. Pick the 1st and 3rd portions.

**ALGEBRA**

√b^4 = b^2 √25 = 5 so, you have √(b^4/25) = b^2/5 = 4 b^2 = 20 so, b = ±√20 Those are the only two real answers. If you want the other two answers, you have to consider that b^2/5 = -4 b^2 = -20 b = ±√20 i

**Algebra**

you are correct. An odd formula, as most such calculations are based on degrees Kelvin.

**pre algebra**

well, geez. You have the formula. Pick any two (x,y) pairs and plug them in: (3-0)/(2+1) = 1 You can see just by looking at the table that when x increases by 1, so does y.

**pre algebra**

What is the slope for the following data? X -1 0 1 2 Y 0 1 2 3 y2 - y1 ---------- x2 - x1 rise / run

**Alegbra**

just solve for t in (1/2)^(t/5730) = 0.75

**alegbra**

so, what's the formula relating distance to amplitude?

**Math**

correct

**Calculus**

well, for f(x) to be differentiable, f'(x) must be defined. Surely you can see that 9x / 2√(3x^2+2) is defined for all real x...

**calculus**

yes, sorry I only gave the volume of the paraboloid, and forgot to subtract the cylinder inside. Better go with MathMate's answer.

**Algebra**

total points scored: 22*88 = 1936 Now we add 5 scores, increasing the total by 3*92 + 2*89 = 454 So, the new average for 27 students is (1936+454)/(22+5) = 88.52

**ALGEBRA**

The sides are in the ratio 1:√3:2, so with the hypotenuse=20, we have 10:10√3:20, with the longer leg opposite the larger angle. Looks like 17.3 to me.

**algebra**

2+4i

**algebra**

2+√-16

**math**

When contesting an answer, it'd be nice if you showed your own steps. I assert that (6x - 3 + 2x/y) * 2xy = (6x)(2xy)-(3)(2xy)+(2x/y)(2xy) = 12x^2y - 6xy + 4x^2 Now, if you just want a single fraction, Only the 2x cancels in all terms in the numerator, and you have 6xy - 3...

**math**

6x - 3 + 2x/y

**ALGEBRA**

why not just say "x+1" instead of "x+4-3"? And if x>=45 works, why not x>=48? or x>=53? I still suspect a typo.

**Math7 Am I right?**

Looks ok to me.

**Science/Math**

I'd say either. If the object is a turkey, chances are it'll be obliterated. If it's a flying block of titanium, it's more likely to have its course altered.

**math**

totals are Px and Ny so, the average we want is (Px+Ny)/(P+N)

**maths**

(a) the -x^2 means it opens downward (b) set x=0 to get y-intercept Since y = (1-x)(x-3) the x-intercepts are easy to see. (c) as usual, the vertex is at x = -b/2a = 1. Find y(1).

**calculus**

The cylinder intersects the paraboloid at z=5. The volume inside the paraboloid is v = ∫[0,2π] ∫[0,2] ∫[0,9-r^2] r dz dr dθ = ∫[0,2π] ∫[0,2] r(9-r^2) dr dθ = ∫[0,2π] 14 dθ = 28π

**Math - eh?**

which two stacks?

**Math (Calculus)**

we've done several of these for you. Got any ideas on this one?

**Algebra**

2h16' = 34/15 hours 4h32' = 68/15 hours Suppose it takes t hours to do the job working together. If the apprentice takes x hours, then it takes Sumi 3/4 x hours. So, we know that 1/t = 1/x + 1/(3/4 x) Also, we are told that (34/15)(1/t) + (68/15)(1/(3/4 x)) = 1 solving...

**math**

yes: (3x+1)(9) = 27x+9

**calculus-answer check**

The chain rule gives 2[(3x^2+1)^3+1] * 3(3x^2+1)^2 * (6x) This is an 11th-degree polynomial, so I suspect your answer is wrong.

**Math**

s = rθ = 13(65 * pi/180) = 169/36 pi

**Math**

r = (a+b-c)/2 5 = (a+b-19)/2 a+b = 29 p = a+b+c = 19+29 = 48

**Math**

If there are x reserved seats, receipts were 1.50x + .05*25x = 2.75x Now, we want y reserved $1 seats to fetch the same money: 1.00y + .05(26x-y) = 2.75x y + 1.3x - .05y = 2.75x .95y = 1.45x y/x = 1.45/.95 = .29/.19 = 29/19 So, now we want y/26x = 29/494 The ratio of reserved ...

**Physics**

well, you have dx/dt = 10cos53.1° = 6 dy/dt = 10sin53.1° - 9.8t = 8-9.8t y = 23.5+8t-4.9t^2 y=0 when t=3.15 At t=3.15, dx/dt = 6 dy/dt = -22.87 so, the speed is √(6^2+22.87^2) = 23.64 m/s Given that, I expect you can do part (b).

**Math**

it appears to be a repeating decimal 0.676767... rounded after 8 decimal places.

**calculus-answer check**

that's the proper method. Using the product rule, y' = (2x+3)(x^2-2) + (x^2+3x)(2x) at x=-1, that's (-2+3)(1-2)+(1-3)(-2) = 3

**Algebra**

1/R = 1/12 - 1/30 1/R = 1/20 R = 20

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