Wednesday

September 2, 2015
Total # Posts: 33,219

**integral calculus**

5(cos3x)^2 but you need a siny to form the full derivative cos^2 u = (1+cos 2u)/2 so, we have 5/2 (cos6x+1) Now you have 5/2 (1/6 sin6x + x) + C
*August 29, 2015*

**maths**

you recall that the sum of the interior angles of a pentagon is 540.
*August 29, 2015*

**Algebra**

t = 7u-8 10u+t = 10t+u-9 I don't get integer values. I suspect a typo.
*August 29, 2015*

**physics**

It takes 3.7 seconds to fall 67.7 meters. So, since time = distance/speed, So, 3.7 + 67.7/v = 3.91
*August 29, 2015*

**Physics**

the normal MKS units, of course.
*August 29, 2015*

**Math**

let's clear fractions and see what we have 5x+3y=3c 4x+2y=c x+y=6 If we subtract the 2nd from the 1st we have x+y=2c x+y=6 that help?
*August 29, 2015*

**Calculus**

(a) might be true (sin(0)/0 not defined) (b) might be true (f(0) might not be defined) (c) must be true (d) must be true - that's the definition of f'
*August 28, 2015*

**Math**

no there are 7 chances for, and 1 against, so 8 chances in all So, p = 7/8 1:7 are the odds against 1/8 is the probability against
*August 28, 2015*

**Maths**

1/6 + 1/5 + 1/4.5 = 53/90 So, their output is in the ratios 15:18:20 20/53 * 750 = 283
*August 28, 2015*

**maths - incomplete**

I don't see any = sign there.
*August 28, 2015*

**Geometry**

no way to tell. If the base is 2, the sides are 17 If the base is 10, the sides are 13. If the base is x, and the sides are y, you know that x + 2y = 36 And, you know that x < 2y or the base is so long that the sides won't reach the ends.
*August 28, 2015*

**good Samaritan school**

918/1030 = 89.12% That means that 10.88% of the berg is showing. so, 224 = 0.1088v
*August 28, 2015*

**math**

(1) 60 is just a number, not a percentage P = 2000 + 60t (2) P is increasing, so you want P = 2000 * 1.05^t 0.95^t means that each year the population decreases by 5%
*August 28, 2015*

**Math**

since 100 is divisible by 4, only the last two digits need to be considered. So, what 2-digit numbers beginning with 4 are divisible by 4? Actually, since 40 is divisible by 4, only the final digit matters. What values less than 10 are multiples of 4?
*August 28, 2015*

**heith**

x + 2x = 30 solve for x; that is the smaller volume.
*August 28, 2015*

**math**

well, you know that density is measured in mass/volume. You are given very little information, so expect the solution to be relatively uncomplicated: 500g/2500cm^3 = 0.2 g/cm^3
*August 28, 2015*

**How many milliliters of a stock solution of 6.00 M**

0.0155L * 1000mL/L = 15.5mL
*August 28, 2015*

**Math**

50 @ SE = <35.36, -35.36> You want a direction θ such that 500 sinθ-35.36 = 0 sinθ = 35.36/500 θ = E 4.05° N
*August 28, 2015*

**Geometry/Steve**

78.5 = 25π, so r=5 (2-2)^2 + (-9-4)^2 = 13^2, so D is wrong (A) (-6-2)^2 + (4-4)^2 = 64, so nope (B) (2-2)^2 + (-1-4)^2 = 25 we have a winner you can check (C) if you want.
*August 27, 2015*

**probability**

0.3 * (1-x) = 0.06 x = 0.80
*August 27, 2015*

**Geometry - eh?**

You said: 14 visited the zoo but not the museum, ... 2 visited the zoo but not the museum. So, which is it?
*August 27, 2015*

**C++**

write a prompt, then read in a real, an integer, and a real
*August 27, 2015*

**Geometry**

the length is correct. But the midpoint is -2+7 = 5. 5 = -2+7 = 12-7
*August 27, 2015*

**Geometry**

Line pb is a line segment on a number line. It has endpoints at -2 and 12. What is the coordinate of its midpoint. My answer would be the total length pf pb is 14 units so the midpoint would be 7.
*August 27, 2015*

**Geometry**

explain how you can use a straight edge and a compass to construct an angle that is both congruent and adjacent to a given angle.
*August 27, 2015*

**Geometry**

If we call the vertices A,B,C and the opposite sides a,b,c then we have (A): a=3, b=4, c=5 (B): a=6, b=√85 stop right there (C): a=13, b=10√2 stop right there (D): a=8, b=10, c=6 we have a winner!
*August 27, 2015*

**Chemistry**

The total masses of S and O are approximately equal, so since O has half the mass/mole of S, that means the empirical formula is probably SO2
*August 27, 2015*

**Geometry**

thank you
*August 27, 2015*

**Geometry**

What is the circumference of a circle in terms of pi with a radius of 2.2? I know that c = 2 pi * r c = 2 pi * 2.2 c = 2 * 2.2 my answer is 4.4 pi
*August 27, 2015*

**Algebra**

actually, that's x ≠ -3y, but it does not affect the final answer. Just sayin' ...
*August 27, 2015*

**Equation - oops. go with Damon**

Hmmm. I seem to have disregarded the distributive property ...
*August 27, 2015*

**Equation**

just use the quadratic formula: x^2 - bx + b-1 = 0 x = [b±√(b^2-4(b-1))]/2 = [b±√(b^2-4b+1)]/2 If you want an integer solution for b, then clearly b=2 and you have x^2-2x+1 = (x-1)^2 = 0 For a real solution, you need b^2-4b+1 >= 0 or b >= 2+&#...
*August 27, 2015*

**Math**

how many even numbers are there? 9 So, P(even) = 9/19 P(4) = 1/19 Now just add 'em up
*August 27, 2015*

**Mathematics**

well, 25kg = 25000 = 250*100 g
*August 27, 2015*

**geometry**

the 3' border on each side increases each dimension by 6. So, the outside dimensions are 18 by 22 Now you can figure the perimeter, right?
*August 27, 2015*

**Math 10**

3^x + 3^-x = 82/9 3^x + 1/3^x = 82/9 (3^2x + 1)/3^x = 82/9 clearly, x=2, but let's go on. 9(3^2x + 1) = 82*3^x 9*3^2x - 82*3^x + 9 = 0 think of this as 9u^2-82u+9, and you get (9*3^x - 1)(3^x - 9) = 0 3^x = 9 or 1/9 x = 2 or -2 aha. an unexpected solution!
*August 27, 2015*

**problem solving.**

j-10 = 4(b-10) j = 2b now it's a cinch, right?
*August 27, 2015*

**math - eh?**

If you mean 2*(1/2)^(4y) = 1/8, then (1/2)^(4y) = 1/16 (1/2)^1 = 1/2 y = 1 well, that didn't work. As written, you have (sort of) (5/2)^(4y) = 1/8 4y log(5/2) = -log8 That's not getting us anywhere. So, just what did you mean? what's the (2 1/2) doing there?
*August 27, 2015*

**nyakasura school**

s = 1/2 at^2, so 1/2 a*64 = 40 a = 80/64 m/s the mass does not matter.
*August 27, 2015*

**math**

for any x, x^2 >= 0 so, y >= 9 for all real x. x can, of course, be any real number. D: (-∞,+∞) R: [9,+∞)
*August 27, 2015*

**algebra**

Where did the 6 yards come from? If the temperature is constant from 6 to 15 yards, then we have to modify things. We then have at x=18 ft (6 yds), t(x) = 52. t(x) = 70-(2/3)x for x in [0,18] t(x) = 52 for x in [18,45] t(x) = 40+3x for x in [45,60] #5. Clearly you meant (x+3)/...
*August 27, 2015*

**algebra**

#4. -8/2 + 4 (____) - 2 -4 + 4x - 2 -6 + 4x that will always be even, so you just want -6 + 4x > 0 4x > 6 x > 6/4 So, any integer greater than 2 will work. #5-7 can be done similarly #8. yes. -16/4 = -4 #9. surely you could easily find out that 3 ft = 1 yd. Geez. So, ...
*August 27, 2015*

**algebra**

what's wrong with -6/9? It's just a fraction. Deal with it 3 - 2(4 - 7) ÷ 9 3 - 2(-3) ÷ 9 3 - (-6)÷9 3 - (-2/3) 3 + 2/3 11/3
*August 27, 2015*

**Calculus 1**

if tanθ = x, then cosθ = 1/√(1+x^2) cos2θ = 2cos^2θ - 1 = 2/(1+x^2)-1 = (1-x^2)/(1+x^2)
*August 27, 2015*

**Calculus 1**

that it is.
*August 27, 2015*

**Calculus 1**

come on. don't forget your trig now that you're taking calculus! You surely recognize cotθ = √3 No? How about tanθ = 1/√3
*August 27, 2015*

**Calculus 1**

for these, always draw the right triangle! for example, sin(arctan 17/8) = 15/17 Draw the triangle, fill in the missing side, and take the needed trig function. Then, as in the second problem here, remember your double-angle formula: sin2θ = 2sinθcosθ
*August 27, 2015*

**Math (functions)**

I believe you are correct.
*August 26, 2015*

**Algebra**

5s + 8(19-s) = 116
*August 26, 2015*

**Algebra**

(1 1/2 - 1 1/8)/2 = (3/2 - 9/8)/2 = (12/8 - 9/8)/2 = (3/8)/2 = 3/16
*August 26, 2015*

**Algebra**

if there are n jr high students, then we have n/(n+100) = 7/9 9n = 7(n+100) 2n = 700 n = 350
*August 26, 2015*

**Ap algebra**

since a function maps values in its domain to values in the range, if the y-value is undefined, the x-value cannot be in the domain. Surely the minimum value of a function is the least y-value in the range. For continuous functions, that is no problem. But, if there are point ...
*August 26, 2015*

**precalc**

y = -4x+1 has slope -4 so do all parallel lines perp. lines therefor have slope 1/4 Now use your point-slope form for the line: parallel line is y-3 = -4(x+2) change the slope to 1/4 for the perpendicular line.
*August 26, 2015*

**Math**

domain is all reals, but since x^2 >= 0 for all x, y >= 9 for all x. That is the range. D: (-∞,+∞) R: [9,∞)
*August 26, 2015*

**Algebra 2**

The angles are 2x,3x,3x. The sum is 180, so x=22.5 C-A = 3x-2x = x
*August 26, 2015*

**Precalc**

check the graph of x^3+1. No horizontal line crosses it more than once, so its inverse is a function. 4^x = (1/2)^(x-3) 4 = 2^2 = (1/2)^-2, so (1/2)^(-2x) = (1/2)^(x-3) -2x = x-3 x = 1
*August 26, 2015*

**Algebra**

15^3
*August 26, 2015*

**AP Calculus**

recall the definition of |u|. It is u for u>=0, and -u for u<0. So, your function f(x) = (x-2)/(x-2) for x >= 2 (x-2)/(-x-2) for x < 2 Now you can easily find the necessary limits. Then, peek at the graph below to verify your calculations.
*August 26, 2015*

**Math**

correct. you can also note that a constant function y(x)=k is the same as y=kx^0, and since 0 is an even power, kx^0 is an even function, and thus symmetric about the y-axis.
*August 26, 2015*

**Precalc**

5x^3 y^-1 z^-5 = 5x^3 / yz^5 take the -3 power of that and you have y^3z^15/125x^9 x^2 y^0 z^-6 = x^2/z^6 square that and you have x^4/z^12 Now just multiply the two fractions and you have y^3z^3 / 125x^5
*August 26, 2015*

**Math**

k is 1000, as in kg, km, etc. 2.0*10^3kcal/day * 1day/86400s * 1000cal/kcal = 23.15 cal/s
*August 26, 2015*

**Math**

.6carat * 200mg/carat * 1kg/10^6mg * 2.205lb/kg * 16oz/lb = 0.00423 oz
*August 26, 2015*

**Geometry**

well, you know that AC+CB=AB, so 3x+55+2x = 65 Now just solve for x and AC=3x
*August 26, 2015*

**math**

divide 36 into 4+5=9 parts. Each part is 4. so, the bikes are 16:20
*August 26, 2015*

**Logs**

well, it is easy enough with a calculator; there's an e^x button. can you use Taylor Series? e^x = 1 + x + 1/2 x^2 + 1/6 x^3 + ... 1 + (-.6) = 0.4 1 + (-.6) + (-.6)^2/2 = 0.58 ...+(-0.6)^3/3!+(-0.6)^4/4! = 0.5494 ...+(-0.6)^5/5!+(-0.6)^6/6! = 0.5488 what other ...
*August 26, 2015*

**geometry**

(-3+x)/2 = -3/2 -3+x = -3 x = 0 Think about it. Starting at -3, x grows by 3/2 to -3/2 at B. It grows by another 3/2 to be 0 at C. (4+y)/2 = 1 4+y = 2 y = -2 Had you plotted these points, you would have seen that your C point was way off. And what's with the "over&...
*August 26, 2015*

**Algebra 1**

I sense a question in there somewhere... x+y=50 20x+30y=1200 so, ...
*August 26, 2015*

**vector**

I see you are not about to do anything more than repost your question. IT'S 90 DEGREES!
*August 26, 2015*

**Math**

D=L D-26 = 2(L-38)
*August 26, 2015*

**math**

oh, come on. You can draw x- and y-axes, surely? They meet at a right angle. How many degrees is that? Just place a pencil pointing out the +x axis, and rotate it till it points upward along the y-axis. You must surely know how many degrees that is. If not, you are in for a ...
*August 26, 2015*

**math**

hint: 1 is on the +x-axis i is on the +y-axis. How far do you have to rotate the +x direction to point in the +y direction?
*August 26, 2015*

**Algebra**

list the x values in the domain, and apply the rule to get y x y=x+1 1 2 2 3 3 4 4 5 Now plot those points and draw a line through them.
*August 26, 2015*

**math**

just start filling in the blanks. Start with xxxxxx greater than 700,000. The choices are 7xxxxx 8xxxxx 9xxxxx my hundred thousands digit is twice my ones digit, my thousands digit,and my hundreds digit. So, the 1st digit must be even, leaving 8x44x4 my remaining digits are ...
*August 26, 2015*

**science**

conserve momentum 20*8 + 10*0 = (20+10)v
*August 26, 2015*

**Geometry**

the diameter of the circle is the distance between the points. That distance is 5. So, now you know the radius is 5/2, and you can take it from there.
*August 26, 2015*

**Geometry**

The endpoints of a diameter on a circle are a(2,1)and B(5,5). Find the area of the circle in terms of 3.14.
*August 26, 2015*

**Geometry**

thank you
*August 26, 2015*

**Geometry**

A garden is 5 ft by 6 ft has a walkway that is 2 ft wide around it. What is the amount of fencing needed to surround the walkway?
*August 26, 2015*

**HELPPPP! ELECTRONICS**

the hole is positive, so it is drawn to the negative pole: the cathode.
*August 26, 2015*

**algebra, numerical operation**

No idea at all? Multiplication comes before addition. Where is that rule violated?
*August 26, 2015*

**Calculus**

BZZT! But thanks for playing. Consider f(x) = 1/(x-a)^2 The limit from both sides is +∞
*August 26, 2015*

**math**

∜500/∜5 = ∜(500/5) = ∜100 = √10
*August 26, 2015*

**math**

11 - 5/(4x-5) There is no "both sides" -- it's a simple expression. Suppose you had 3 - 2/5 You put it all over the denominator: (3*5-2)/5 Same here: (11(4x-5)-5)/(4x-5) = (44x-60)/(4x-5)
*August 26, 2015*

**Math**

you need √((8-4)^2 + (y-3)^2) = 11 √(16+(y-3)^2) = 11 16+(y-3)^2 = 121 (y-3)^2 = 105 y-3 = ±√105 y = 3±√105 you can check this by noting that the locus of all points a distance of 11 from (4,3) is a circle: (x-4)^2 + (y-3)^2 = 121 Now pick...
*August 26, 2015*

**math**

1 radian is 180/π degrees, so ...
*August 26, 2015*

**Trig**

This kind of problem works very well when you draw the pertinent triangle. If cosθ = 12/13, you have a 5-12-13 triangle, so sinθ = 5/13 Similarly, sinθ = 3/5 gives you a 3-4-5 triangle, so tanθ = 3/4
*August 26, 2015*

**mathematics**

2x^2 - 5x - 2 = 0 x = [5±√(25+16)]/(2*2)
*August 26, 2015*

**Math**

We can without loss of generality assume a=1, so (1+4d)/(1+2d) = (1+16d)/(1+4d) d = -5/8 The AP is 1, 3/8, -2/8, -7/8, -12/8, -17/8, -22/8, ... -9 The GP is 1, -5/8, 25/64, ... (-12/8)/(-2/8) = 6 (-9)/(-12/8) = 6
*August 26, 2015*

**Math**

can you find x when x^2 = 4? x^2 = 9? Does 144 have two equal factors?
*August 26, 2015*

**Math**

well, each cm represents 5m, so 9cm --> 5m * 9 = 45m now do 7cm the same way.
*August 26, 2015*

**Math - eh?**

If you say so.
*August 26, 2015*

**Math**

The width grows by the same ratio as the height, so w/8 = 30/14
*August 26, 2015*

**Calculus**

x^2+y^2+6x-8y+9 = 0 rearrange things a bit to get ready to complete the squares: x^2+6x + y^2-8y = -9 x^2+6x+9 + y^2-8y+16 = -9+9+16 (x+3)^2 + (y-4)^2 = 16 so, the center is at (-3,4) with radius 4. Note that the center is 4 units above the x-axis, so C touches the x-axis at...
*August 26, 2015*

**Math-Trigonometry**

Assuming B is between A and the mountain, then the height h is found from h cot22° - h cot40° = 125
*August 26, 2015*

**MATH**

n^0 = 1 for all nonzero n. So, you just have x^3x^4 = x^7
*August 26, 2015*

**MATH**

well, just plug in the numbers: 2^5*2^8/1^5 = 2^13 = 8192
*August 26, 2015*

**algebra**

since there are two corners cut from each side, the volume is 3(x-6)(x-6)
*August 26, 2015*

**Lccn acardamy**

well, first off, mercury is a metal. A simple google search will provide a wealth of interesting explanations.
*August 26, 2015*

**pre algebra**

20-2*7+1+(3)+10 20-14+4+10 6+4+10 10+10 20 In order to get your answer, you'd need 20-(14+4+10) Also, online you should use * for multiplication, so you don't get things mixed up with decimal points, as in 2.7
*August 26, 2015*