Tuesday

January 27, 2015

January 27, 2015

Total # Posts: 28,405

**Physics**

300rev/min / (1/120 min) = 36000 rev/min^2 Now you can convert that to whatever units you like. Remember: 2pi radians/rev
*December 11, 2014*

**math**

2(w + 2w) = 72
*December 11, 2014*

**math**

xy=20 x+y = x + 20/x minimum occurs where x=2√5 (same as the problem for finding maximum area for a given perimeter: a square) So, pick two integers near √20. They would be 4 and 5, with sum=9 The only other sums are 1+20=21 2+10=12
*December 11, 2014*

**Pre-Calc**

Note that if you multiply on the left inside the radical, by (1-sinx)/(1-sinx), you have √((1-sinx)^2/(1-sin^2(x)) That should get you most of the way there, since √x^2 = |x|
*December 11, 2014*

**trig**

well, the perimeter is the sum of the sides, so 3n-4 + 3n+9 + 4n+5 = 114 10n = 104 Now it's easy to find n, and then figure the actual side lengths.
*December 11, 2014*

**statistics finding the shaded region**

enter your data here. http://davidmlane.com/hyperstat/z_table.html It's a great Z table site.
*December 11, 2014*

**Algebra 2**

well, note that f(x) = 5(x^3-2^3) = 5(x-2)(x^2+2x+4) That help?
*December 11, 2014*

**statistics probability**

P(-1.39<=Z<=1.69) = 0.8722 You can play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
*December 11, 2014*

**Math**

If the mother's age is x, x/2 - 10 = 12 x = 44
*December 11, 2014*

**maths**

log_2(a) = 2log_4(a) = 3log_8(a) So, you have 2/(1/3 log_2(a)) - 4/log_2(a) = 1/(1/2 log_2(a)) 1/log_2(a) (6 - 4) = 2/log_2(a) 6-4 = 2 Or, recall that log_b(a) = 1/log_a(b) So, you have 2log_a(8) - 4log_a(2) = log_a(4) But, since 8=2^3 and 4=2^2, that means 6log_a(2) - 4log_a(...
*December 11, 2014*

**algebra**

log_8(2)+log_8(4x^2) = 1 1/3 + log_8(4) + log_8(x^2) = 1 1/3 + 2/3 + log_8(x^2) = 1 log_8(x^2) = 0 x^2 = 1 x = ±1 ln2 - ln(3x+2) = 1 ln (2/(3x+2)) = 1 2/(3x+2) = e 2/e = 3x+2 x = (2/e - 2)/3 = 2(1-e) / 3e ln(x-3) - ln(x-5) = ln 5 (x-3)/(x-5) = 5 x-3 = 5x-25 x = 11/2
*December 11, 2014*

**algebra**

well, clearly the spacing indicates -e^(-3.9n-1) -1 = -3 e^(-3.9n-1) = 2 -3.9n-1 = ln2 n = -(1+ln2)/3.9 Of course, I could be way off...
*December 11, 2014*

**Math**

since 36=6^2 its exponents are only half as big as powers of 6 to get to the same value. That is, log_36(n) = 1/2 log_6(n) So, 1/log_36(a) = 1/ (1/2 log_6(a)) = 2/log_6(a)
*December 11, 2014*

**Algebra 2**

remember the difference of cubes, and you see that you have (2x)^3 - (10y^2)^3 (2x-10y)((2x)^2+(2x)(10y^2)+(10y^2)^2) = 2(x-5y)(4x^2+20xy^2+100y^4) = 8(x-5y)(x^2+5xy^2+25y^2)
*December 11, 2014*

**Middle School Math**

Not at all. 3g+5 = 17 3g+5-5 = 17-5 3g = 12 3g/3 = 12/3 g = 4 I'd be interested to see how you arrived at -20.
*December 11, 2014*

**math**

If the ratio is 2:3, then games won = 2/5 of 120 = 48 So, games lost is 3/5 of 120 = 72 The correct proportion would be x/120 = 3/5 Consider. If the ratio is 2:3, the won/lost = 2/3 won = 2/3 lost lost+won=120 lost + 2/3 lost = 120 5/3 lost = 120 lost = 120 * 3/5 = 72
*December 11, 2014*

**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*

Pages: <<Prev | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | **11** | 12 | 13 | 14 | 15 | 16 | 17 | Next>>