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February 28, 2015

February 28, 2015

Total # Posts: 29,289

**math show work please**

You just need 2^(t/7) = 3 (t/7) log2 = log3 t = 7log3/log2 = 11.1 hours
*December 11, 2014*

**algebra**

that would be the cost per ride, since the only thing that changes is the number of rides.
*December 11, 2014*

**Math**

You are correct. 4 was indeed the solution to the equation, but you correctly went on to realize that that meant the actual price was $8/mug. Good work. Still, just plugging x=4 into the equation would have given the same answer for the income, since that accounted for the ...
*December 11, 2014*

**Math**

It would surely help if you showed how you got there. What you provide is not much help. If x is the number of price increases, then we have price p = 6.00 + 0.50x quantity sold q = 200 - 10x revenue is price * quantity, so r(x) = (6.00 + 0.50x)(200-10x) = 1200+40x-5x^2 This ...
*December 11, 2014*

**Math**

no, the amplitude is the coefficient out front: 37 You know the amplitude of sin(x) is 1 5 in this case isn't really anything. It might look like a phase shift, but it's not even that. And you still have a typo, since there's no t anywhere on the right side. You ...
*December 11, 2014*

**Trig**

so, since when is 1/2 pi not the same as pi/2?
*December 11, 2014*

**Math**

diameter is 35, so radius is 17.5 -- that is the amplitude of f(t) f(t) is like 17.5 sin(t) Since the max height is 50, that means the axle is at 50-17.5 = 32.5 f(t) is like 17.5 sin(t) + 32.5 The period of sin(kt) is 2pi/k, so we need 2pi/k = 13 k = 2pi/13 f(t) = 17.5 sin(2pi...
*December 11, 2014*

**Algebra**

well, just plug in the numbers and see whether it's true. 5(-2) - 2(-1) + 1 > 0 -10 + 2 + 1 > 0 -7 > 0
*December 11, 2014*

**Math**

since the range of sin(x) is [-1,1] that is the domain of sin^-1(x).
*December 11, 2014*

**Math**

In no way! 3/12 = 25% 50% is 6/12 !
*December 10, 2014*

**Math**

there were 12 plants in all 3 had no fertilizer. 3/12 had no fertilizer. Is C your final answer? ...
*December 10, 2014*

**trigonometry**

A. 4.5/x = tan 25° B. 4.5/x = sin 25°
*December 10, 2014*

**math**

121 = 7+2x
*December 10, 2014*

**Math 6th grade**

3 1/4 = 15/4 pizzas each person got 1/4 * 15/4 = 15/16 of a pizza Joe ate 1/4 of his portion, so he ate 1/4 * 15/16 = 15/64 of a pizza Extra credit: who stole the other 3/4 of a pizza? No one buys 3 1/4 pizzas!!
*December 10, 2014*

**Math**

Actually, since -(-(-x)) = -x we have |-x| = -x which is true for all x <= 0 Still the correct answer, though.
*December 10, 2014*

**Math solve the equation**

7x = 72 7x/7 = 72/7 x = 72/7 9p = 30 p = 30/9 or 10/3
*December 10, 2014*

**German**

yes, but it is incorrect. das Kind ein Kind no "eine" allowed. And, since Kind is a noun, it is always capitalized. Now, with adjectives, following a definite article, they are all ending in e. Otherwise, they are inflected by gender: das kleine Kind ein kleines Kind...
*December 10, 2014*

**Algebra2**

I'd be interested in seeing your work. I get (h-6)/150 = tan 46.2° (h-6)/150 = 1.04 h-6 = 156.42 h = 162.42
*December 10, 2014*

**Algebra2**

If the height is h, then (h-6)/150 = tan 46.2°
*December 10, 2014*

**pre-algebra**

5n >= 300*1.25 + 500 5n >= 375+500 n >= 175
*December 10, 2014*

**Calculus**

y = e^-x^2 y" = (4x^2-2)e^-x^2 y"=0 when x = ±√2 y(±√2) = e^-2 = 1/e^2 = 1/e^a Looks like a=2
*December 10, 2014*

**math**

The first train travels 16(6 37/60) = 96 592/60 = 105 13/15 min = 105'52" or 1 hr 45 min 52 sec do the other similarly
*December 10, 2014*

**Math**

y' = 7x^3+28x^2-63x-252 = 7(x+4)(x+3)(x-3) Now things should be easy. You know y is increasing when y' > 0...
*December 10, 2014*

**Algebra**

even-root radicals have domain only positive reals, since even powers of all numbers are positive odd powers can be negative or positive, so odd-root radicals have domain all reals.
*December 10, 2014*

**Math**

80/x + 80/(x+10) (80(x+10)+80x) / x(x+10) (160x+800) / x(x+10)
*December 10, 2014*

**Pre-Calc/Trig...**

by definition, ln(e^x) = x e^(lnx) = x ln and e^ are inverse operations. Just as cos(arccos(x)) = x √(x^2) = x a*(x/a) = x a+(x-a) = x So, ln e^4.3 = 4.3 e^(ln 4.3) = 4.3
*December 10, 2014*

**Math**

hint: -9x^2-55x+56 = (7+x)(8-9x)
*December 10, 2014*

**Math**

you are correct
*December 10, 2014*

**math**

h√-1
*December 10, 2014*

**Math**

5.815 < 6.021
*December 10, 2014*

**calculus**

s(t)=250-3t+9t^2+2t^3 v(t) = -3+18t+6t^2 a(t) = 18+12t plug in t=0 for initial values. the other questions are just normal ideas. What do you get?
*December 9, 2014*

**Math**

factors: 1,2,3,6,7,14,21,42 So, which add to -19? 2-21
*December 9, 2014*

**help asap**

well, find the slopes of AC and BD. If their product is -1, they are perpendicular.
*December 9, 2014*

**math**

17(2+3) = 17(5) = ?
*December 9, 2014*

**AP Calc**

a = pi d^2 when a=3, d^2 = 3/pi v = pi/6 d^3 dv/dt = pi/2 d^2 dd/dt So, -pi/18 = pi/2 (3/pi) dd/dt dd/dt = -pi/27 in/min
*December 9, 2014*

**Calculus- Tangent Line**

looks good to me. Of course, it would help to know just what the curve was ...
*December 9, 2014*

**Math**

x^2+4x = x(x+3) 2x^2+13x+15 = (2x+3)(x+5) x^2-16 = (x-4)(x+4) So, what you have is x(x+4)(x+5) ------------------ (2x+3)(x+5)(x+4)(x-4) That leaves you with x / (2x+3)(x-4)
*December 9, 2014*

**Math**

72x^7
*December 9, 2014*

**Statistics**

10P4 = 10*9*8*7
*December 9, 2014*

**fuctions and statistics**

you can always multiply by 1 without changing anything. You know that 1 ft = 0.3048 m That means that 1ft/0.3048m = 1 0.3048m/1ft = 1 Now, you want to convert feet to meters, so just multiply by the "correct" representation of 1, so that the units cancel out as you ...
*December 9, 2014*

**English**

They look ok to me. And yes, "according to" is ok, as well. I guess you are all "set" now, eh?
*December 9, 2014*

**English**

#2 is correct, except for the typo. I'd never use "the" in this case. However, it is correct to say He must have been late for the bus. A bus is a specific vehicle, but "school" is a more vague entity, implying education and other activities, and not ...
*December 9, 2014*

**Physical Science**

All oxygen boils at -183 C, but I have no idea what temperature your oxygen is at.
*December 9, 2014*

**math(5th grade)**

zero, if the school is north of his home.
*December 9, 2014*

**Calculus**

well, you remember that inflection is where y" = 0 concave up when y" > 0 For y" I get 2 times your answer, but that doesn't change its properties. y' = 2cosx(sinx+1) y" = -sinx + cos^2x - sin^2x = -sinx + 1 - 2sin^2x = -(2sinx-1)(sinx+1) Note ...
*December 9, 2014*

**Calculus**

the line has slope 2/3 So, the normal needs slope -3/2 3x^2-4y^2=8 6x - 8yy' = 0 y' = 3x/4y So, we need 3x/4y = -3/2 y = -x/2 3x^2-4(-x/2)^2 = 8 3x^2-x^2 = 8 x = ±2 y = ∓1 So, we want lines through (2,-1) and (-2,1) with slope -3/2 y-1 = -3/2 (x+2) y+1 = -...
*December 9, 2014*

**Calculus**

I suspect a typo. Why the ^1 ? At x=0, you have (1+0)^1/0 = 1/0 = +∞
*December 9, 2014*

**Math**

g(x) --> -6x^2/5x^2 = -6/5
*December 9, 2014*

**Math (Word Problem into formula)**

To start with, there is 1 kg of tin. After adding x kg of tin, then we have c(x) = (x+1)/(x+6)
*December 8, 2014*

**algebra**

the first thing is your sloppy typing. a/b - c/d is NOT (a-b)/(c-d)
*December 8, 2014*

**geometry**

18ft8in = 224in So, one side is 56in area = 56^2 in^2 Now convert that to ft^2
*December 8, 2014*

**GEOMETRY**

T(3+4),(5-4) = T7,1
*December 8, 2014*

**Calculus**

Hmmm. Not surprising, since you have not posed a question ...
*December 8, 2014*

**geometry**

you need to note that one pace is one yard. Now the instructions should make sense, since 15 paces is halfway from 3rd base to 2nd.
*December 8, 2014*

**geometry**

the stride is one yard. So, the bases are 30 paces apart. 15 paces is halfway between the bases, along the baseline. Then move back 3 paces from the baseline. Done.
*December 8, 2014*

**Calculus**

naturally, since that is the formula for the sum of a G.P.
*December 8, 2014*

**Calculus**

The sum is 1/(2^i) = 1/2^1 + 1/2^2 + 1/2^3 + ... = 1/2 + 1/4 + 1/8 + ... You will recognize that as a geometric series, with S = (1/2)/(1 - 1/2) = 1
*December 8, 2014*

**Algebra 2**

See the graph at http://www.wolframalpha.com/input/?i=solve+x^2+-+3x+%3D+1
*December 8, 2014*

**Algebra 2**

well, 5*2 = 8+2
*December 8, 2014*

**Algebra 2**

x^2-2x-35 = 0 Well, the factors of 35 are 5 and 7. They differ by 2, so ...
*December 8, 2014*

**Math Help**

all correct. good work.
*December 8, 2014*

**Fraction**

13 = 12 8/8 minus 7 5/8 equals 5 3/8
*December 8, 2014*

**calculus**

if the dimensions for metal and wood are m and w, then we know that cost = 2(10w+20m)=400 area = m*w = m(200-20m)/10 = 20m-2m^2 This is just a parabola with its vertex at m=5 So, the maximum area is with dimensions metal=5 ft wood=10 ft
*December 8, 2014*

**12 Math**

log_2(36)^3 = 3log_2(36) = 3(2+log_2(9)) = 6+6log_2(3) Not sure where you want to go from there. Now, if you meant log(32), that is 5, so log_2(32^3) would be 15.
*December 8, 2014*

**College Algebra**

DRS says there are 2 or 0 positive roots 1 negative root RZT says look for roots among ±1,5,7,35 Synthetic division using easy values first says f(x) = (x-1)(x^2-2x-35) I think you can probably take it from there, ok?
*December 8, 2014*

**Linear Algebra**

maximize r = 500x + 750y + 1000z subject to x+y+z <= 30 x/2 + y + 2z <= 3*8 The answer from the above constraints may in fact not allow for proper distribution among operating rooms, so watch out for that.
*December 8, 2014*

**math**

The bottom is +289
*December 8, 2014*

**Math**

what do you mean simplify? You can distribute the fraction, and you get -15/20.5 = 0.73 so you could write -.73x^2 - 2.20x - 1.65 but that's only approximate. SO, again, what do you mean by "simplify"? I will note that x^2+3x+2.25 = (x+1.5)^2 if that helps You ...
*December 8, 2014*

**Math**

12x^12/4x^3 = 3x^9 x^8/24x^6 = x^2/24 3x^9 * 24/x^2 = 72x^7
*December 8, 2014*

**Homeschool**

each 1.5 cm represents 3m So, how many times bigger is 8 than 1.5? There will be that many 3m lengths. So, the real length is 8/1.5 * 3
*December 8, 2014*

**trig**

you can't solve it. It's just a function definition. But, the graph is at http://www.wolframalpha.com/input/?i=r+%3D+3%281-sin%CE%B8%29 Now, if you want to see its equation in rectangular coordinates, r = 3 - 3sinθ r^2 = 3r - 3r sinθ x^2+y^2 = 3r - 3x x^2+y^2...
*December 8, 2014*

**math**

40*40 = 1600 So, the cost is (800/9)*25 + 800*2.50
*December 8, 2014*

**math**

if $x at 8%, then the rest (8000-x) is at 12%. So, .08x + .12(8000-x) = 650 Now do the math.
*December 8, 2014*

**Algebra 2**

clearly there are (2y^2+6)/(y^2-1) notebooks. So, plug in y=3 to find how many.
*December 8, 2014*

**Math**

you get the y-intercept when x=0 You get the x-intercept when y=0. So, 1/6 x^4 - 2x^2 + 4 = 0 x^4 - 12x^2 + 24 = 0 x^2 = (12±4√3)/2 = 6±2√3 So, take each of those values and get its ± square roots.
*December 8, 2014*

**fundamental to programing**

read x,y,z if (x<y & x<z) {print x} else if (y<x & y<z) {print y} else {print z}
*December 8, 2014*

**Math (TRIG)**

Review the equation for a hyperbola in polar coordinates. #2 Hint: sec^2 = 1 + tan^2 #3 y = 500 sin70° t - 16t^2 Solve for t when y=0 to find the time in flight The x-velocity is constant at 700 cos70° So using the time from step 1, distance = speed * time
*December 8, 2014*

**Trig (math)**

#1 in polar form, -1+√3i = (2,2π/3) So, the two square roots of that are (√2,π/3) and (√2,4π/3) #2,#3 just plug in x = r cosθ y = r sinθ #4 8x - 7y = -10 7y - 8x = 10 7r sinθ - 8r cosθ = 10 r = 10/(7sinθ-8cosθ)
*December 8, 2014*

**math**

well, 2 2/3 = 2.66 2.75 = 2.75 5/2 = 2.50 So, which is least?
*December 8, 2014*

**math**

24 = 6*4 42 = 6*7 So, 6 people each clean 4 small and 7 large cages. No other larger number divides both 24 and 42, since 4 and 7 have no common factors.
*December 8, 2014*

**Algebra**

If there are n games, you want .40*.80n + p*.20n = .50n .32 + .20p = .50 .20p = .18 p = .18/.20 = .9, or 90% Check. If there are 100 games, you have won 32 already. So, there are 20 games left, and you need to win 18 of them, or 90%
*December 7, 2014*

**Trig (math)**

#1 You have y = 9 x = 9√3 So, tanθ = 1/√3 r = 18 You should be able to recognize a 30-60-90 right triangle... #2 (4*5)cis(30°+120°) #3 is just the same. #4 is the same, but divide r, and subtract angles.
*December 7, 2014*

**calculus**

Just plug in the numbers you have, and you get (20)(10)(5) + (20)(15)(3) + (10)(15)(8) = 3100 How did you come up with 265?
*December 7, 2014*

**Math**

the distance s = 1/2 at^2 So, 500 = 4.9t^2 Now you have the time. You need to say what the velocity's direction is. As you recall, s = vt + 1/2 at^2 It makes a big difference whether v is positive or negative. In 5 seconds it will fall 4.9*5^2 meters.
*December 7, 2014*

**L'Hopitals Rule**

sin(x^2-4)/(x-2) --> 2xcos(x^2-4)/1 --> 4 ln(x-3)/(x-5) --> (1/(x-3))/5 -> 0 (x-pi/4)tan(2x) = (x-pi/4)/cot(2x) --> 1/(-2csc^2(2x)) = -1/2 sin^2(2x) --> -1/2
*December 7, 2014*

**linear approximation**

f'(x) = -24x sin(3x^2) f'(0) = 0 So, you want the line with slope=0 through (0,4). Duh. y=4 Kind of a dumb place to approximate, eh? With a horizontal tangent, and all that.
*December 7, 2014*

**Pre Calc Take 2**

Hmmm. Let's try that again without the typo... log (x-6)*(x+3) = 1 x^2-3x-18 = 10 x^2-3x-28 = 0 x = (3±11)/2 x = -4 or 7 The only real solution is x=7 Check: log(1)+log(10) = 1 yes
*December 7, 2014*

**Pre Calc**

well, work it out... log(x-6)+log(x+3) = 1 log (x-6)*(x-3) = 1 (x-6)*(x-3) = 10 x^2-9x+18 = 10 x^2-9x+8 = 0 (x-1)(x-8) = 0 x = 1 or 8 x=1 does not work, because then x-6 < 0 and the log is not defined. So, the only real solution is x=8 Check: log(2)+log(5) = 1 log(10) = 1 ...
*December 7, 2014*

**Algebra 1**

Describe how the graphs of y =IXI nand ym = IXI -15 are related. 1- the graphs have the same shape,. The y intercept of the 2nd graph is -15 2-the graphs have the same y intercept. The 2nd graph is steeper than y= absolute x 3- the 2 graphs are the same 4- the graphs have the ...
*December 7, 2014*

**Algebra 1**

Graph y= absolute x -2
*December 7, 2014*

**solve**

since time = distance/speed, if the speed was x, 168/(2x) = 168/x - 3 x = 28
*December 7, 2014*

**Advanced Algebra**

Since we have a geometric series, Sn = A * (e^knt - 1)/(e^kt - 1) So, plug in the numbers and we have S5 = 0.5 (e^(-0.853*4*5)-1)/(e^(-0.853*4)-1) = 0.517
*December 7, 2014*

**math**

23 min * 100/3 rev/min = 766.666 rev So, divide the distance between the 1st and last grooves into 767 grooves, and you get 4/766.666 = 0.0052 inches between grooves So, you have an arithmetic sequence with a = 5.75*2π d = 0.0052*2π and you want S767 Just plug and chug
*December 7, 2014*

**problem solving**

If there were n bricks at price p, then we know that 1.05np = 315 (n+6)p = 315 Now just eliminate p and solve for n.
*December 7, 2014*

**Maths**

There is a lot of missing information here. I can easily devise a scenario where the assertion is false. Suppose A is 1 cm above L and B is 10 cm above L. If D and E are on L, clearly CD < CE.
*December 7, 2014*

**AP CALC. AB**

#2 (a) is correct #3 f' = lnx + 1 The only extremum is at x = 1/e f" = 1/x, which is positive at 1/e, so f(1/e) is a minimum. Looks like (c) is the answer See the graph at http://www.wolframalpha.com/input/?i=x*lnx Ignore tha part where x<0, since lnx is not real ...
*December 6, 2014*

**Pre calculus**

look up the half-life of C-14. If it is k years, then the amount left after t years is (1/2)^(t/k) So, you want to solve for t in (1/2)^(t/k) = 0.289
*December 6, 2014*

**math**

a + c = 8 3.5a + 2.5c = 23 Now just solve for a and c.
*December 6, 2014*

**math**

the LCD(2,3) is 6. So, multiply the whole equation by 6: 3x-30 = 2
*December 6, 2014*

**Algebra**

Heck, they gave you an example, so that makes it easy. Just pick any values for a,b,c: 9-3=6 ==> 9*6<+>-3*6=9*-3 or 54<+>-18=-27 Who cares what <+> really means?
*December 6, 2014*

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