Friday
April 18, 2014

Posts by STEVE


Total # Posts: 21,761

Calculus
as usual, draw a diagram and you will see that if θ=0 when x=0, tanθ = x/4 so, sec^2θ dθ/dt = 1/4 dx/dt Now, you have θ and dθ/dt, so just solve for dx/dt

Calculus
At time t, using the law of cosines, d^2 = (7t)^2 + (5t)^2 - 2(5t)(7t)cosπ/4 = 74t^2 - 35√2 t^2 = (74-35√2)t^2 so, 2d dd/dt = 2(74-35√2)t Now, plug in your numbers to get d(15), and solve for dd/dt at t=15 Remember to use appropriate units

algebra
if so, y/x is constant 6.4/4 = 1.6 11.2/7 = 1.6 16/10 = 1.6 looks good, no?

Calculus
what you have tried is the volume when rotating the region about the x-axis. But, of course, the volume of a disk is pi r^2 dx, not pi r^3 dx In addition, your radius is 3-x, not y, since you are rotating about the line x=3, not y=0. So, if you want to use discs, you need to i...

Calculus- typo
64/6 + 8 + 20 - ( -64/6 + 8 -20 ) 64/3 + 0 + 40 184/3

Calculus
product rule and chain rule -- if y = uv y' = u'v + uv' Here u=csc^2 x and v = arccos(1-x^2) y' = -2 cscx cscx cotx arccos(1-x^2) + csc^2 x 1/√(1-(1-x^2)^2) * -2x kind of messy, no? well, recall that if cos u = 1-x^2, sin u = x, so we really have y = -csc...

math
13/150

Math
84 = pi * 36 * h now just solve for h same for the other

Calculus Help
just use the quotient rule and chain rule. If f = u/v f' = (u'v-uv')/v^2 f' = 5(8x-3)^4(8)(6x+7)^12 - (8x-3)^5(12)(6x+7)^11(6)]/(6x+7)^24 = -16(8x-3)^4(21x-31)/(6x+7)^13

math studies
The diagonals are perpendicular, and they bisect each other. So, you have 4 right triangles with legs 6 and 3.5 The diagonals bisect the vertex angles, so the angle is 2arctan(6/3.5)

Algebra
If a+b = c you cannot say that a^2+b^2 = c^2 √(9y - 196) + √196 = √49 √(9y - 196) + 14 = 7 √(9y - 196) = -7 But, √N is positive. So, you cannot have √(9y - 196) = -7 √x(√9 - 4/3) = √25 √x(3 - 4/3) = 5 √x(5...

Algebra
x=.10(100-x) x = 10 - x/10 11/10 x = 10 x = 100/11

Chemistry - incomplete
A good first step would be to get some H on the left . . .

Math
the difference is 32 votes Had 16 people voted differently, they'd both have had 228 votes. So, if at least 17 had voted differently, Susan would have won.

Algebra
There's no way that √28 + √63 + √175 = 6.06 You must have hit some wrong keys Just a rough approximation would be 5 + 8 + 13 = 26, not 6.06!

Algebra
#1 ok #2 ok if you meant √(6p+1) #3 √28 + √63 + √175 2√7 + 3√7 + 5√7 = 10√7 #4 √(2w+5) + 4 = √25 √(2w+5) = 1 2w+5 = 1 2w = -4 w = -2 #5 √18/√(8-3) 3√2 / √5 (3√10)/5 If you meant ...

Algebra
check the discriminant #1: b^2-4ac < 0, so no solutions #2: b^2-4ac = 0, so one solution

Algebra
let's say that f(x) = a√x + b Then we know that a√1 + b = -2 a√5 + b = 0 a(√5-1) = 2 a = 2/(√5-1) = (√5+1)/2 b = -2 - (√5+1)/2 = -(√5+5)/2 f(x) = (√5+1)/2 √x - (√5+5)/2 Somehow I don't think that's w...

Mathh
squares: 1 4 9 cubes: 1 8 27

math. plzz help
√(3^2+5^2) = √34 so the slant height is 5.8 √(10^2+4^2+10^2) = √216 = 14.7 √(14^2+3^2+4^2) = √221 = 14.9

Algerbra
factors of 18 which differ by 3 are 3 and 6, so w(w-6)(w+3)

Math
If Ling, suitcase, and backpack weigh x,y,z, respectively, then we have x = 3y y = z+20 x+y+z = 170 so, 3y + y + y-20 = 170 5y = 190 y = 38 So, Ling weighs 114 suitcase: 38 backpack: 18

math
(100*40+(53-83))/100 = 39.7

chemistry
each mole of CaCO3 produces 1 mole of CaO so, convert grams CaO to moles, then back to grams of CaCO3

math
(22.8+9.5)(1800/285)(3.49) = $711.96

math
158-110 = 48 degrees so, it will take 96 seconds

math
12-23-10-74-77

Algebra 1
units: 0-8 tens: 1-9,2-9,...8-9,9 9+8+7+...+1 = 45

algebra
if there were a adults, there were 2a children, so 8*a + 5*2a = 648 18a = 648 a = 36 36 adults and 72 children

Math
2 walls are 9x8 2 walls are 7x8 ceiling is 9x7 2(2*9*8 + 2*7*8 + 9*7)/275 = 2.32 so, 3 cans of paint

math
3^n: 1,3,9,27 so, which is 5 times that? Hint: only one sequence starts with 5

math
p'(1)=0 so max or min p"(1) < 0, so concave down: a max (A)

math
we know x is not going to infinity, so the asymptote must be vertical. (D)

math
x(6x+1) < 15 6x^2 + x - 15 < 0 now you have a parabola. You need to find where it crosses the x-axis, and between those two points, it will lie below the x-axis. (2x-3)(3x+5) < 0 so, the roots are at x = -5/3 and 3/2 Between those two values, the parabola lies below t...

Algebra II
√(-24 - 10i) If you want to find a perfect square which equals -24-10i, it will have to include -5i, so (a-5i)^2 = -24-10i a^2 - 10ai - 25 = -24-10i Hmmm. Looks like a=1 (1-5i)^2 = 1 - 10i - 25 = -24-10i So, √(-24 - 10i) = 1-5i or -1+5i Or, if you use polar form, y...

rational expressions
not sure what you are after Do you mean the equation must use two different expressions, both of which are equal to the given value, or do you mean the equation must use two rational expressions, and the result is the given value? as in 1/(2x+1) - 3x/(x^2+5) = (x+5)^2

calculus
The circle in the x-y plane is x^2 + (y - a/2)^2 = a^2/4 x^2 = a^2/4 - (4y^2-4ay+a^2)/4 = (y^2-ay)/4 The limits of integration in the x-y plane are 0 < y < a 0 < x < (1/2)√(y^2-ay) then use symmetry and multiply by 4

Algebra 1 Answer Check
Looks good to me.

algebra
6n-(-10) = -20 6n = -30 n = -5

Math
a = pi * (25/2)^2 Nothing was said about lawn furniture (or tents).

Math (check answers)
I think #1 is D to convert from cm to m, you divide by 100

math
could be any of the choices, depending on the unseen and unexplained diagram.

Math
no diagram, but if angles 1,2,3 are consecutive vertices, then 15x + x+y = 180 x+y + 3z = 180 15x = 30z Nope; impossible answer. So, some explanation is needed

Geometry
17x = 408 x = 24

Calculus
the answers are the same √[(x-3)/2] = √[(x-3)/2 * 2/2] = √(2x-6)/2

Math 2
360 = 10*36 The factors of 36 are 1,2,3,4,6,9,12,18,36 Pair them up to get your answer.

Math 2
w is 1,2,3,4,5 v = 2*5*w = 10w, so possible values are 10,20,30,40,50

math
s^2 = r^2 + h^2 = 16+81 = 97 s = 9.8

Math 2 questions
5.7 x/4 = 20/10 x = 8 you are correct. Too bad it was a guess, not the result of calculation.

plane geometry
a = 1/2 r^2 (θ-sinθ) 4.3 = 1/2 * 4 (θ-sinθ) θ-sinθ = 2.15 Solve using your favorite numerical or graphical method to get θ = 2.63511

Math help plz check my answers!
It is, in fact, A a rectangle can be long and skinny, 4 sides not equal.

Math - Nope
Bzzt. no two sides of a trapezoid have to be equal. Think harder.

Math help plz check my answers!
and we have a winner!

Algebra 1 Answer Check
looks good to me

math
95 said something 70+45=115, so 20 said both

math
If he bought x in January, 2x+3 = 15 x=6

Physics
solve 2π√(L/g) = 1/7

Alegbra
-7-2z^3+4y -12-3z^3+6y --------------- -19-5z^3+10y

Alegbra - eh?
they're already in scientific notation.

Alegbra
36.92x10^(13-22) 36.92x10^-9 3.692x10^-8

math
you must have some examples in your text. You can get some good info here: http://www.purplemath.com/modules/plane2.htm

Math
assuming you want to expand the product, you get 6p^2 + 29p + 9 Play around some at calc101.com -- click on the long multiplication button. multiplying polynomials is just like multiplying numbers, where the power of the variable is like the 1s,10s,100s,... columns in numbers....

Math (check answers)
I think 1A would be in cm, not meters. A pencil is rather short. The others look ok.

Pre-Algebra
i agree

multiplication
well, is 2*3 at least 7?

Music help
The minor key starts three semitones below its relative major, so A major -> F# minor 5# = FCGDA, so key = B

math
for this, you need to recall that the perpendicular bisector of a chord goes through the center of the circle. So, if you can find two of the bisectors, they will intersect at the center. To find the bisectors, locate the midpoint of a chord, then find a line perpendicular to ...

Math
Take a look at http://www.jiskha.com/display.cgi?id=1394471353 and plug in your points instead

Math - hmmm
Actually, the above is true only if DF=DG. I think there's something missing here.

Math
No idea where O is, but if you meant FG=15x, then since FDG = FDE, FE=FG, so 9x+114 = 15x 4x = -114 x = -26

algebra 1
42

Math
2^x = 10^5

programming
total=0 n=10 for (i=1..n) total += test[i] avg = total/n

math - incomplete
no function given.

trig
h/80 = sin 40°

algebra
4y + 5y^2 + 2y^3 - 8y^2 collect like powers to get 2y^3 - 3y^2 + 4y

Calculus
Since the derivative is the slope of the tangent line, we need -2sinx - 2cosx*sinx = 0 -2sinx(1+cosx) = 0 sinx = 0 means x = nπ cosx = -1 means x = (2n+1)π so, f(x) has a horizontal tangent at x=nπ

math
1098

math
y = -5(x-1)^2 + 4

math
the 13x in the middle indicates you will need 5 as one of the factors of 20, and it cannot be multiplied by 2, so (2x+5)(x+4)

Calculus Help
3/31: t=90 4/21: t=111 L'(t) = 2.8cos[(2π/365)(t − 80)](2π/365) now just plug in t=90 and t=111 The answer, of course, will be in hr/day.

math
we know that x+1 = -x+7 x=3 so the base is 6

Math
2/5 of males = 2/5 * 30 = 12 That should help.

Math
2 pi *10 inches per hour

Math
(1610-1250)/(3*10)

Math
x(1/2 + 1/4 + 1/9) = 62

Math
150 * 3 * 1/2 * density.of.snow

Math
x+y = 3/2 x-y = 5/12 2x = 11/12 ...

Math
C MN and PR are not corresponding sides

MATH TRIGO-PLSSS ANSWER CLEARLY COZ IM VERY LOW IN
Draw a diagram. Let T be the top of the tower M be the top of the monument A be the base of the tower B be the base of the monument ∠TBA = 31° so, 145/TB = sin 31° Since ∠TBM = 59° ∠MTB = 18°, ∠TMB = 103° The desired height (MB) is f...

algebra
c(p) = 50+2p

algebra
well, is (2+3)^2 = 2^2+3^2 ? Hint: (x+y)^2 = (x+y)(x+y) expand that and compare to x^2+y^2

math
take a look at http://www.wolframalpha.com/input/?i=3%28x-4%29^2+-3+

math
since there are 5 choices for each digit, there are 5^8 choices for the number

Math
if the initial value is v, v - .35(2) = 13520 Now, knowing v, after n years the car is worth v(1 - .35n) Note that the car is fully depreciated after only 3 years, if the depreciation is 35% of the full value each year.

math trig
If B is at distance x from the tower of height h, h/x = tan 46° h/(x+80) = tan21° so, eliminating x, we get h/tan46° = h/tan21° - 80 Now just solve for h

MATH :DD
2(5+.12(m-200)) < 30 minimum? 0 of course.

Maths
x = (y-3)/5 d = (c+2)/5 a = (v-u)/t

science
neutral must have 11 so, the +1 ion has only 10 electrons p+n = 23 p = atomic number

science
an ion has unbalanced charge, so what do you think?

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