# Posts by STEVE

Total # Posts: 54,358

Math
Vs*Ts = 88 (Vs-13)(Ts+4) = 72 22*4 = 88 9*8 = 72

Physics
add the two velocities in a right triangle. ?(1^2+3^2) = ?10 mi/hr 300 yds = 300/1760 = 0.17 miles so, it will take 0.17 hours to cross the river. Since the river flows 3 times as fast as he swims, he will wind up 3*0.17 = 0.51 miles downstream.

calculus
correct

calculus
yes. since 3=?3*?3, ?3/3 ?3/(?3*?3) = 1/?3

calculus
3cotx - ?3 = 0 3cotx = = ?3 cotx = 1/?3 Now it's time to review the "standard" angles whose trig functions are easy to remember. One of these is 60°, where cot60° = 1/?3

Math plz help
#2. Remember that |x| = x if x >= 0 |x| = -x if x < 0 So, you have |y+4| < 1 so, either y+4 >= 0, meaning y >= -4 or y+4 < 0, meaning y < -4 If y >= -4 y+4 < 1 y < -3 If y < -4 -(y+4) < 1 -y-4 < 1 -5 < y But also, we started with y <...

Math plz help
clearly not 2D. Just plug in y=2 |2+4| = |6| = 6 Bzzzt #3 is also wrong. You forgot to divide by 2. |2r| = 12, not |r| = 12 #4 is correct

Math
There is no unique solution. This is just the equation of an hyperbola. Some integer solutions are (-3,3) (0,-9) (1,19) (4,7) y = (10x+9)/(2x-1)

fire dynamics
no idea. how fast does it burn?

fire dynamics
1 gallon = 231 in^3. The fuel depth in the spill is volume/area: 3500*231/2500? = 102.94 in so, at 6 in/hr, it will burn for 102.94/6 = 17.157 hours

algebra
KE = 1/2 mv^2 2KE = mv^2 m = 2KE/v^2 C = 0.5x+10 C-10 = 0.5x x = 2C-20

Bart made some home improvements for \$6,091 using a six-month deferred payment plan with an interest rate of 23.79%. What is the balance after the deferment period if no payments are made? A.\$6,091.00 B.\$6,776.90 C.\$7,540.05 D.\$6,852.40 My answer is D

Jeffrey earned a gross income of \$51,280 last year. He made \$1,746.83 in student loan interest deductions, donated \$2,914 to his favorite charities and paid \$3,941.47 in home mortgage interest. Jeffrey claims a standard deduction of \$11,400 for himself and his non-working ...

math
well, only b is rational ...

Pre-Calculus
If x is liters and y is gallons, then y = kx k = 14/53 now plug in y=25 Or, since the ratio is always the same, and you have (25/14) as many gallons, you will have (25/14) * 53 liters

Pre-Calculus
w = kz so, w/z = k, a constant. So, you want w such that w/3 = 9/-6

Pre-Calculus
well, y=kx, so plug in the values.

Pre-Calculus
true.

Geometry
well, the diagonal of a square of side s is s?2, so what do you think?

math
126423746278

algebra
3+4a+6b-8-5 4a+6b + 3-8-5 now do you get it?

Maths
48 = 8*6, so 8 times as much flour. 8 * 3/5 = ?

AP Calculus
d is false. The others are all true. See http://www.wolframalpha.com/input/?i=(5x%5E3-5x%5E2-10x)%2F(2x%5E5-2x)

Physical
.2 cm^3 * 2.7g/cm^3 * 6.02*10^23atoms/27.0g = 1.204*10^22 atoms

math
One number is x, the other is 31-x 2/3 x = 5/8 (31-x) Now just solve for x and you're almost done

Maths
1/4 of 4/5 is 1/5, so 3/5 remain in the tank 3/5 * 32 = ?

math
0.37x = 0.0925 x = 0.0925/0.37 = 0.25

Physics
how long does it take to fall 1.02m? 4.9t^2 = 1.02 the horizontal speed does not matter.

Maths
You sure there are not 17 balls? Then the probabilities would be 8/17 and 9/17 Much messier with 18 balls, but you can see how to divide it up.

Math
This has popped up two or three times in the last few days. Don't know why it doesn't appear in the list of related questions. Try here: https://www.jiskha.com/display.cgi?id=1506885649

physics
watts = energy/time so, use this to find the energy (watch the units!) PE = mgh

Chemistry
9.45?m = 9.45*10^-4 cm each inch is 2.54cm so, 9.45*10^-4cm * 1in/2.54cm = ? in

Chemistry
how many meters in 0.45 miles? If that number is N, then it will take (N/1500)*(14'34.56")

math
There are lots of useful online calculators. One such, for this topic, is at http://www.zweigmedia.com/RealWorld/LPGrapher/lpg.html

Algebra 1
|| is ALWAYS positive h(1) = |1-7*1| = |1-7| = |-6| = 6 h(9) = |1-63| = |-62| = 62 remember!!! |N| = N if N >= 0 |N| = -N if N < 0

Algebra 1
nope. g(9) = -9^2+10*9-3 = -81+90-3 ... g(-1) = -(-1)^2+10(-1)-3 = -1-10-3 ... g(-3) = -(-3)^2+10(-3)-3 = -9-30-3 ...

Geometry
where are H and J in relation to R and N?

Calculus
#1 f(x) = (1-x)/(1+x) and g(x) = x/(1-x) f(g) = (1-g)/(1+g) = (1-(x/(1-x))/(1+(x/(1-x)) = 1-2x while the domain of 1-2x is all reals, g is undefined for x=1, so that must be excluded from the composite as well. #2 multiply by the "conjugate" (?(x^2+8)-3)/(x-1) * (?(x...

Algebra 1
correct

Algebra 1
since I have no idea what f is, and g(x) contains no other x's, it's hard to say. Try proofreading before posting.

Algebra 1
just plug in the values for x everywhere in the equation. f(60) = 9/5 * 60 + 32 = 108+32 = 140 and so on

Physics
It does not matter how far away the person is standing (as long as it's not 0 distance!). If you draw a ray from the top of the person to the mirror and back to the person, the point that the person sees is exactly twice as far down as where the reflection is in the mirror...

Math
hard to say, since you don't show your work. One way is substitution. x = 7-5y-3z, so using that in the last two equations, you get 2(7-5y-3z)+y+4z = 1 2(7-5y-3z)-y+2z = 1 shuffling things about, that gives 9y+2z = 13 11y+4z = 13 Now, since 2z = 13-9y, use that to get 11y+...

Calculas
If you meant what you wrote, then the domain is all reals except x=0 If you meant y=1/(x-7) then the domain is all reals except x=7. In other words, all reals except where the denominator is zero.

maths
100/25 x^9/x^5 y^5/y^4 = 4x^4y

math
just look up the conversions. For example, 39.5 ft * 1yd/3ft = 13 1/6 yd 47tsp * 1cup/8tsp = 5 7/8 cup

Math problem help
doubling the 1st equation, we have 6/x + 4/y = 4/3 8/x - 4/y = 2/9 add them up to get 14/x = 14/9 x = 9 Now just plug that in to get y=6

math
1/2 + 1/3 = 5/6 2/3 of the remaining 1/6 is 1/9 That means that 1/18 is left x/18 = 20 x = 360

seems like this one went by yesterday. But, it's not in the related questions, so, ignoring the hint, we have x^2+y^2+z^2 = 9 3x^2-y^2-z^2 = 7 0x^2+y^2+2z^2 = 6 adding #1 to #2, we have x^2+y^2+z^2 = 9 4x^2+0y^2+0z^2 = 16 so, 4x^2=16 --> x^2 = 4 --> x = 2 Since all ...

College Algebra
s = q-4 In 7 years, then, (q+7) + (q-4+7) = 64 ...

maths
to find x, solve 5^2 + (x+5)^2 = (x+8)^2 25+x^2+10x+25 = x^2+16x+64 6x+14 = 0 x = -7/3 So, the area is (5)(5-7/3) = 5*8/3 = 13 1/3 m^2

Math
f?g = f(g) = g^2+2g-8 = (2x-6)^2+2(x-6)-8 now just expand that out if you must.

maths
a = 1/2 r^2 ? 12 to 4 is 1/3 of the way around, so the area is 1/2 * 3.5^2 * 2?/3 = 6.125? cm

maths
so, change 7-2 to 7-(-2) geez

maths
8.1*10^7 / 9*10^2 = (8.1/9)*10^(7-2) = 0.9*10^5 = 9.0*10^4 he would have had 3/4 of the origianl amount, or 3/4 * 300 = 225

Physics
s = 1/2 at^2, so 1/2 * 0.5 * t^2 = 100 t^2 = 400 t = 20 s assuming the acceleration is in m/s^2

maths
2^(3x) = 2^(5x-9) 3x = 5x-9 2x = 9 x = 9/2 10^x = 10000 = 10^4 x = 4

Maths
cotA = cosA/sinA cosA = cotA/cscA = cotA/?(1+cot^2 A)

Math
Try using math symbols. I believe you meant f(x) = x^4-4x^3-8x^2-7x+1 No idea what "Tapos" means, but 2x^3+5x^2-10x+16 used as a divisor does not leave a remainder of 3. Also, what does "k" have to do with any of the other stuff? Maybe you can fill in the ...

linguistics
Q: What is the difference between theory and practice? A: In theory, there is no difference, but in practice, there is.

Math
the same - both are linear measurements

Algebra
If y = mx+b, plug in the points to get 1/2 m + b = -3/2 -1/2 m + b = 1/2 add them together to get 2b = -1 b = -1/2 subtract them to get m = -2 y = mx+b = -2x - 1/2 or, consider the slope of the line: (y2-y1)/(x2-x1) = (1/2+3/2)/(-1/2-1/2) = -2 Now use the point-slope form to ...

Math
the price alone was 100% of what was paid, so what was added?

Math
the change was \$1 so, what fraction of \$4 is that? or, 5/4 = 1.25, so 5 = 1.25 * 4

Maths
The two courses are 90 degrees apart, so it's just a matter of figuring the angles of the right triangle. If the angle made by the 1st ship is ?, then the bearing of ship 2 from ship 1 is just (157+180-?)°

math
Assuming that the 1st letters are in sequence around S, the angles follow LSO=LSP+PSO PSN=PSO+OSN That means LSP+PSO=PSO+OSN so LSP=OSN Now just change that to a 2-column proof.

Geometry
Huh? That is the definition of a linear pair -- the two angles form a straight angle.

Math
"sin" is often used as a shorthand way of writing sin? technically, "sin" by itself is just the name of the function, and it has no value until a ? is specified. Sometimes when manipulating a long equation or expression, the ? is assumed throughout, and not...

Algebra
on the number line, > (greater) means "to the right of" < (less) means "to the left of so, you wold graph it by shading everything to the right of -5 AND to the left of 2 In other words, the segment between -5 and 2 ... -6 -5 (...) 2 3 ...

algebra
5s-3p = fp+12 5s = 3p+fp+12 5s-12 = (3+f)p (5s-12)/(3+f) = p

Physics
conserve momentum. That means m1*v1 + m2*v2 = mv 25*8 + 55*0 = (25+55)v

thank you

I disagree. If she claims the standard deduction, she cannot file a Schedule A as well, so she cannot deduct the interest and charity. I pick C

Amanda earned a gross income of \$37,250 last year. She made \$489.78 in IRA contributions, donated \$782 to her favorite charity and paid \$1,276.65 in home mortgage interest. If Amanda claims a standard deduction of \$5,700 and her exemption is \$3,650, what is her taxable income...

maths
see "neha"'s post -- the one after yours...

maths
just plug and chug a+b = 2cosx+i sinx + 2cosy + i siny = 2(cosx+cosy) + (sinx+siny)i Now, (sinx+cosx)^2 = sin^2x+2sinx cosx+cos^2x = 1+2sinx cosx similarly, (siny+cosy)^2 = 1+2siny cosy Since 2^2-b^2 = (a+b)(a-b), we have (sinx+cosx)^2 - (siny+cosy)^2 = ((sinx+cosx)+(siny+cosy...

Algebra
6000r = 390 r = 390/6000 = 0.065 or 6.5%

Chemistry
Say you have 1 gram of Lithium. If x grams have mass 6.02, then 6.02x + 7.02(1-x) = 6.94 x = .08 so, 8% of Li is the lighter isotope. Makes sense, since 6.94 is so much closer to the heavier value.

Physic
I thought it was 42 ...

Geometry
Rubbish. Did you actually plot the points? Let's call the midpoint M. M is just as far from A as it is from B. So, if you consider the coordinates, M-A = B-M Or, B = 2M-A = 2(2,-9)-(4,10) = (4,-18)-(4,10) = (0,-28) Or, in other words, moving from A to M caused x to go from...

geometry
Surely you can see that the exterior angles of regular polygons with a different number of sides cannot be the same. Try drawing something easy, like a square and a pentagon. As you travel around the outside of a polygon, you keep turning by the same angle. One trip around ...

Math
but first change .1x to .01x ...

Math
for (2-x) > 0, f(x) = 1 for (2-x) < 0, f(x) = -1 so, no zeros, domain is all reals except x=2, range is {-1,1} http://www.wolframalpha.com/input/?i=%7C2-x%7C%2F(2-x)

Math
no idea. what is the function?

math
blank must be an even digit

algebra 2
no idea. what is the objective function?

Math
12/-4 = -3 -26/12 = -3 so, clearly An+1 = An * -3 Now you know you have a = -4 r = -3 and use your formula to get the 5th term.

Math
Let u = sin^3(x) du = 3 sin^2(x) cos(x) dx dv = e^(2x) v = 1/2 e^(2x) ?u dv = uv - ?v du = 1/2 e^(2x) sin^3(x) - 3/2 ?e^(2x) sin^2(x) cosx dx = 1/2 e^(2x) sin^3(x) - 3/2 ?e^(2x)cosx dx - 3/2 ?e^(2x) cos^3(x) dx Pull the same trick again, and you will have 3/4 of the original ...

Math
you need to get rid of that pesky ln(1+x). So, u = ln(1+x) du = 1/(1+x) dx dv = x dx v = 1/2 x^2 ?u dv = uv - ?v du = 1/2 x^2 ln(1+x) - 1/2 ?x^2/(1+x) dx which is not so hard, eh?

Math
?x^3 cos(x^2) dx If you let u=x^2, you have du = 2x dx and the integral is 1/2 ?[?/2,?] u cos(u) du Now you can tackle that using integration by parts.

Math
x sinx cosx = 1/2 x sin2x u = x/2 du = 1/2 dx dv = sin2x dx v = -1/2 cos2x ?u dv = uv - v du = -1/4 x cos2x + 1/4 ?cos2x dx = -1/4 x cos2x + 1/8 sin2x + C using the limits of integration, we have (-1/4 ? + 0) - (0 +0) = -?/4

Math
Cute. Let u = xe^(2x) du = e^(2x)(1+2x) dv = 1/(1+2x)^2 v = (-1/2)/(1+2x) ?u dv = uv - ?v du = -(xe^(2x))/(2(1+2x)) - ?(-1/2)e^(2x) dx = -(xe^(2x))/(2(1+2x)) + e^(2x)/4 = e^(2x)/(4(1+2x)) + C

Sharon purchased a sprinkler system for \$1,950 using a six-month deferred payment plan. The interest rate after the introductory period is 23.99%. No down payment is required, but there is a minimum monthly payment of \$25. What is the balance at the beginning of the seventh ...

Krystal bought a refrigerator from a rental center for \$1,050. She makes 16 monthly payments of \$112.75 with her credit card. The rental center charges \$1.25 for every purchase made with a credit card. What is the total cost of the refrigerator? My answer is \$1824 dollars \$112...

Pre-Calculus
Oops. sin/cot = sin*tan = sin^2/cos csc/cot = 1/sin * sin/cos = 1/cos You should have said csc(2x)/cot(2x) - sin(2x)/cot(2x) = 1/cos(2x) - sin^2(2x)/cos(2x) = (1-sin^2(2x))/cos(2x) = cos^2(2x)/cos(2x) = cos(2x) or, csc-sin = (1-sin^2)/sin = cos^2/sin = cos * cot

Pre-calc
16/(2x+2) = 8/(x+1)