Saturday

January 21, 2017
Total # Posts: 37,341

**Calculus**

let the edge be x cm long V = x^3 dV/dt = 3x^2 dx/dt = 3x^2 (3) = 9x^2 cm^3/s so when x = 1 dV/dt = 9(1) cm^3/s do the 2nd part in the same way

*November 2, 2016*

**calculus**

let the height be h ft then diameter = 3h ft, and the radius is 3h/2 V = (1/3)? r^2 h = (1/3)? (9h^2/4)(h) = (3/4)? h^3 dV/dt = (9/4)? h^2 dh/dt when h = 15, dV/dt = 10 10 = (9/4)? (15) dh/dt dh/dt = 40/(135?) ft/s = 8?/27 ft/s

*November 2, 2016*

**Math, Precalc**

3^x + 5^(x+3) - 3^(x+4) + (1/3)5^(x+2)= 0 3^x(1 - 3^4) + 5^(x+2)(5 + (1/3)(1) ) = 0 -80(3^x) + (16/3)(5^(x+2) = 0 times -3/16 15(3^x) - 5^(x+2) = 0 15(3^x) = 5^(x+2) divide by 5 3(3^x) = 5^(x+1) 3^(x+1) = 5^(x+1) this can only be true if x = -1 that is, if 3^0 = 5^0 , which ...

*November 2, 2016*

**Math, Precalc**

Sue's time riding the bike = 5/15 hrs = 1/3 hr Sue's time walking the 2 miles = 2/3 hr total time = 2/3 + 1/3 = 1 hr total distance = 7 miles average speed = 7/1 = 7 mph

*November 2, 2016*

**Maths**

let the number of sides be n each interior angle = 180(n-2)/n each exterior angle = 360/n 180(n-2)/n < 10(360/n) by 84 180(n-2)/n = 10(360/n) - 84 times n, which is positive 180(n-2) = 3600 - 84n 180n - 360 = 3600 - 84n 264n = 3960 n = 15 sum of angles = 180(15-2)° = ...

*November 2, 2016*

**word problem**

48/16 = 3 72/12 = 6 so I can draw 18 rectangles of 12 by 16 on a piece of 48 by 72 BUT, using a regular saw there will be a saw-cut waste and that changes the question. I will assume your question is ignoring the sawdust.

*November 1, 2016*

**Pythagorean theorem**

depends on what the question is.

*November 1, 2016*

**Calculus**

f''(x) = x^2 f'(0) = 8, f(o)=4 if f''(x) = x^2, then f'(x) = (1/3)x^3 + c for the given: 8 = (1/3)(0) + c ---> c = 8 , and f'(x) = (1/3)x^3 + 8 f(x) = (1/12)x^4 + 8x + k f(0) = 4 4 = (1/12)(0) + 8(0) + k ----> k = 4 f(x) = (1/12)x^4 + 8x + 4 ...

*November 1, 2016*

**Calc**

height = -4.9t^2 + 10t + 2 d(height)/dt = -9.8t + 10 = 0 at max height 9.8t = 10 t = 10/9.8 height = -4.9(10/9.8)^2 + 10(10/9.8) + 2 = appr 7.102 m is the max height when it reaches the ground 0 = -4.9t^2 + 10t + 2 4.9t^2 - 10t- 2 = 0 t = (10 ± ?139.2)/9.8 = 1.306 ...

*November 1, 2016*

**math**

each side of first one is 848/4 or 212 cm each side of the 2nd is 436/4 or 109 cm so the area of the first = 212^2 cm^2 = 44944 cm^2 the area of the 2nd is 109^2 cm = 11881 cm^2 total area = 56825 cm^2 each side is ?56825 = 5?2273 and the perimeter = 20?2273 = appr 953.52

*November 1, 2016*

**Math**

p + pr(12) = 2p p(1 + 12r) = 2p 1 + 12r = 2 12r = 1 r = 1/12 = appr .08333.. or 8 1/3% consider $100 in 12 yrs, at a rate of .083333..., we would have 100 + 100(.08333..)(12) = 200 check!

*November 1, 2016*

**Maths**

(3/4) / 2 = 15/x (3/4)x = 30 x = 30(4/3) = 40 or notice: sugar : butter = 3/4 : 2 = 3 : 8 so 15:x = 3:8 3x=120 x=40

*November 1, 2016*

**mathematics**

ones digit ---- x tens digit -----x+3 x+x+3=13 x = 5 ----> x+3 = 8 so the number is 85

*November 1, 2016*

**math**

let's first handle 75 degrees tan75 = tan(30+45) , skipping the degree symbols = (tan30 + tan45)/(1 - tan30tan45) = (1/sqr3 + 1)/(1 - (1/sqr3)(1)) = (sqr3 + 1)/(sqr3 - 1) tan 75 = 2tan(75/2)/( 1 - tan^2 (75/2) ) let tan(75/2) = x for easier typing (sqr3 + 1)/(sqr3 - 1) = ...

*November 1, 2016*

**math**

What is 3(2 1/4) inches = 3(9/4) inches = 27/4 inches or 6 3/4 or 6.75 inches

*November 1, 2016*

**Algebra**

We don't "guess" in mathematics. just translate the English to Math: (1/2)m + (1/3)s = 11 times 6, the LCD 3m + 2s = 66 ** 6 years from now: (m+6) + (s+6) = 40 m + s = 28 *** 2 times *** ---> 2m + 2s = 56 subtract from ** m = 10 back in *** 10 + s = 28 s = 18 ...

*November 1, 2016*

**algebra--miss sue**

small correction: the in-equation should be (p - .2p) - 50 â‰¤ 150 or .8p - 50 â‰¤ 150 check: .8p â‰¤ 200 p â‰¤ 200/.8 or p â‰¤ 250 phone could cost $250 less 20% or less $50 means cost ...

*October 31, 2016*

**math 142**

reading past the strange symbols: 1,000 are deposited into an account quarterly for eight years at an interest rate of 7.878 % compounded quarterly. How much is in the account at the end of the 8 years? i = .07878/4 = .019695 n = 32 amount = 1000(1.019695^32 - 1)/.019695 I got...

*October 31, 2016*

**Algebra**

number of tens --- x number of fives --- x+4 number of twenties -- 2x-3 now for their value: 10x + 5(x+4) + 20(2x-3) = 290 solve for x, sub back into my definitions

*October 31, 2016*

**Algebra**

width --- x length --- 2x+4 x(2x+4) = 286 2x^2 + 4x - 286 = 0 x^2 + 2x - 143 = 0 (x+13)(x-11) = 0 x = 11 or x = -13, the last part is not possible the width is 11, the length is 26 check: 26 is 4 more than twice 11 area = 11(26) = 286

*October 31, 2016*

**algebra**

smallest --- x middle ---- x+10 largest ---- 3x x + x+10 + 3x = 180 etc

*October 31, 2016*

**Adv. functions**

You should know these identities: sin(Ï€+x) = -sinx e.g. sin 210° = sin(180°+30°) = -sin30° cos(Ï€/2) - x) = sinx e.g. cos(60) = cos(90-30) = sin30 cos(Ï€+x) = -cosx e.g. cos 210° = -cos30° sin(3Ï€/2 + x) = -cosx ...

*October 31, 2016*

**Math**

The standard formula amount = paym( (1+i)^n - 1)/i assumes that payments are made at the end of a payment periods, yours are made at the beginning of each period. I will pretend we have 145 payments, but then subtract the last one i = .046/12 = .003833... (I stored in my ...

*October 31, 2016*

**maths**

Why did you repost all those questions again, they had all been answered http://www.jiskha.com/display.cgi?id=1477910441

*October 31, 2016*

**maths**

http://www.jiskha.com/display.cgi?id=1477910197

*October 31, 2016*

**Maths**

http://www.jiskha.com/display.cgi?id=1477909974

*October 31, 2016*

**maths**

http://www.jiskha.com/display.cgi?id=1477909541

*October 31, 2016*

**maths**

http://www.jiskha.com/display.cgi?id=1477909333

*October 31, 2016*

**math**

I read that as: (secØ - tanØ)/(secØ + tanØ) = 1/4 4secØ - 4tanØ = secØ + tanØ 3secØ = 5 tanØ 3/cosØ = 5sinØ/cosØ 5sinØcosØ = 3cosØ 5sinØcosØ - 3cos&...

*October 31, 2016*

**Math**

So if there are only two tests, (x+54)/2 = 74 x+54 = 148 x = ..

*October 31, 2016*

**Maths**

for any n-gon, the sum of interior angles is 180(n-2) °

*October 31, 2016*

**Maths**

Did you make your sketch ? Two concepts are needed here: 1. the slope of perpendicular lines are negative reciprocals of each other 2. You have to know how to find the distance between two points. 1. slope of AB = (9-1)/(3-5) = -4 so slope of AC = + 1/4 but slope of AC = (y-5...

*October 31, 2016*

**maths**

One of the most basic concepts in this topic is "finding the slope between two points" Your text and notes MUST contain the steps I will do the first one, you do the rest slope = (y2-y1)/(x2-x1) = (6-5)/(-4-1) = 1/-5 or - 1/5

*October 31, 2016*

**maths**

I will do the first one, you do the other two in the same way. Let P(x, y) be on AB so that AP/PB = 1/2 for the x: (x-1)/(-4-x) = 1/2 2x - 2 = -4 - x 3x = -2 x = -2/3 for the y: (y-3)/(-1-y) = 1/2 2y - 6 = -1 - y 3y = 5 y = 5/3 so P is (-2/3 , 5/3) for b), I am sure you meant...

*October 31, 2016*

**MATHS URGENT PLEASE HELP**

midpoint between (x1, y1) and (x2, y2) = ( (x1+x2)/2 , (y1 + y2)/2 ) a) so C = ( (4+6)/2 , (-3-2)/2 ) = (5 , -5/2) b) use the method I just showed you in the previous post to find the two length, show them equal.

*October 31, 2016*

**MATHS URGENT PLEASE HELP**

Just use your formula Dist = √(x2-x1)^2 + (y2-y1)^2 ) = √( 6-1)^2 + (10-(-5))^2 ) = √(25 + 225) = √ 250) = √25 * √10 = 5√10 Do the 2nd one in the same way

*October 31, 2016*

**intermediate algebra**

1. smaller number --- x larger number --- x+8 (1/2)(x+8) + (1/4)x = 22 etc 2. son's age 10 years ago --- x man's age 10 years ago ---- 3x in 12 years, son's age = x+22 in 12 years, man's age = 3x+22 x=22 = (3/5)(3x+22) etc 3. Let job to be done be 1 unit let A...

*October 31, 2016*

**MATH PLEASE HELP!!!**

1. (3/4)z + 6 = (3/4)(x + 8) check by expanding 2. 18x + 6y = 6(3x + y)

*October 30, 2016*

**Permutations**

In the majority of texts the word "committee" usually denotes combinations, that is there is no specific order. In that case the result would be C(11,3) which is 165 But you titled your post "permutations", so Steve's answer would apply for that ...

*October 30, 2016*

**Math**

one rotation = 2πr = 28π inches = 28π/12 or 7π/3 ft or appr 7.33 ft number of rotations to go 440 ft = 440 ÷ (7π/3) = 1320/(7π) or appr 60.024 rotations time at 15 rotations per min = (1320/(7π)) / 15 = 4 minutes

*October 29, 2016*

**math**

prob(defect) = 3/12 = 1/4 prob(working) = 3/4 prob (5 of 5 are working) = C(5,5) (3/4)^5 (1/4)^0 = 243/1024 prob(3 work, 2 don't work) = C(5,3)(3/4)^3 (1/4)^2 = 10(27/64)(1/16) = 270/1024

*October 29, 2016*

**math**

prob(backup system works) = prob(1 of 2 generators work) + prob(both will work) = C(2,1)(.98)(.02) + C(2,2) (.98)^2 = .9996

*October 29, 2016*

**Maths**

Key point: When they pass each other they both will have traveled the same time let the distance covered by the faster car be x km distance covered by slower car = 400 - x km time of faster car = x/90 time of slower car = (400-x)/70 (400-x)/70 = x/90 (400-x)/7 = x/9 7x = 3600...

*October 29, 2016*

**math**

This is an AP, where a = 12, and d = 2 sum(6) = (6/2)(24 + 5(2)) , using our formula = 3(34) = 102 or ... if you don't know what an arithmetic sequence is: day1 = 12 day2 = 14 day3 = 16 day4 = 18 day5 = 20 day6 = 22 add them up to get 102

*October 29, 2016*

**PreCal**

b = -(4-√3) = (-4 + √3) then b^2 = 16 - 8√3 + 3 = 19 - 8√3 Bob had 15-8√3 for that part modify his solution.

*October 28, 2016*

**macomb**

You have no exponents in your original question. Ms Sue's answer is correct for the question you typed. did you mean −8^−1 + 8^−2 ? then = 1/-8 + 1/8^2

*October 28, 2016*

**Algebra**

You did not post the sequence

*October 28, 2016*

**math**

A = 2 pi r (r+h) A = 2π r^2 + 2πrh A - 2πr^2 = 2πrh h = (A - 2πr^2)/(2πr)

*October 28, 2016*

**math**

You probably meant to type: y = (2x^2 - 5)/(3x^2 - 4) ok, what about it?

*October 28, 2016*

**Math**

I have no idea how you got .1446.. 12% ---> 0.12 17% ---> 0.17 3% ---> 0.03 add them up to get 0.32

*October 28, 2016*

**Math**

area = 4(2/3) ft^2 = 8/3 ft^2

*October 28, 2016*

**Math**

Both the first and the third are given in terms of the 2nd, so we will let the second be our base variable let the 2nd be x then the first is 3x and the third is 10x 10x - 3x = 1050 7x = 1050 x = 150 sub back into my definitions and add them up

*October 27, 2016*

**Math**

Ms Sue's answer is the correct one.

*October 26, 2016*

**Differential calculus**

y=(√e^x)/x y = (e^(x/2) )/x dy/dx = (x(1/2)e^(x/2) - e^(x/2) )/x^2 simplify if needed.

*October 26, 2016*

**Differential calculus**

what kind of root? square root ? is it √(e^x/x) or (√e^x) / x ?

*October 26, 2016*

**Differential calculus with analytic geometry**

xy^2+4y^3=x-2y x(2y)dy/x + y^2 + 12y^2 dy/dx = 1 - 2dy/dx dy/x(2xy + 12y^2 + 2) = 1 - y^2 dy/dx = (1 - y^2)/(2xy + 12y^2 + 2)

*October 26, 2016*

**Math**

Use a Venn diagram, put in all the data values, and your answers can just be read from the diagram

*October 26, 2016*

**Calculus**

2x^2y-3y^2=-11 4xy + 2x^2 dy/dx - 6y dy/dx = 0 dy/dx(2x^2 - 6y) = -4xy dy/dx = -4xy/(2x^2 - 6y) at (2,-1) dy/dx = -4(2)(-1)/(8 -6(-1)) = 8/14 = 4/7 equation of tangent: y+1 = (4/7)(x - 2) massage it any way you need to

*October 26, 2016*

**Algrebra**

To visualize the different cases, why not give yourself an actual point. e.g. 2) let (x,y) = (-4,5) <---- had to be in quadrant II then (-x,y) = (4,5) , which is in first quadrant (x,-y) = (-4,-5) , in the third (-x,-y) = (4,-5) , in the fourth

*October 25, 2016*

**Algebra**

number of tens ---- x number of fives ---- x+2 number of twenties -- 2x-3 value equation: 10x + 5(x+2) + 20(2x-3) = 445 10x + 5x + 10 + 40x - 60 = 445 55x = 495 x = 9 sub into my definitions ...

*October 25, 2016*

**Math**

each side of the base ---- x ft height of box ------------ y ft x^2 y = 8 y = 8/x^2 cost = 6x^2 + 4xy = 6x^2 + 4x(8/x^2) cost = 6x^2 + 32/x

*October 25, 2016*

**Algebra**

second number ----- x first number ------- 2x - 183 solve for x: x + 2x-183 = 1161

*October 25, 2016*

**Math**

let the longer piece be x cm then the shorter piece is 14-x cm 14-x = (2/5)x times 5 70 - 5x = 2x 70 = 7x x = 10 the long piece is 10 cm, the shorter is 4 cm check: is 4/10 = 2/5 ? , YES

*October 25, 2016*

**math**

Most direct way: The volume of the rock equals the change in the volume of the tank. The change in the height was 4 cm. So the volume of the rock is (9)(15)(4) cm^3 = 540 cm^3 or, along your thinking volume of tank at the start = (9)(15)(8) or 1080 cm^3 volume after rock is ...

*October 25, 2016*

**math**

I have no idea what your x and y stand for, but in a rhombus, opposite angles are equal and adjacent angles add up to 180° So the other angle is 130°

*October 25, 2016*

**Math**

assuming 30 days in a month ... cost of one can per day from machine = 30(.75) = $22.50 cost using 12-pack = (4.99/12)(30) = 12.48 continue

*October 25, 2016*

**Algebra 1**

1. A - wrong 2. C - wrong 3. B - wrong 4. A - wrong How did you get your answers? Where you just guessing?

*October 25, 2016*

**Algebra 1**

I don't see any choices or any work Surely you don't expect somebody to just go ahead and do this assignment for you , do you? e.g. what steps would you take to answer the first one?

*October 25, 2016*

**Mathematics**

Just use your definitions: "first term of an Arithmetic Progression is -4" --> a=-4 "the 15th term is double the 5th" ---> a+14d = 2(a+4d) a + 14d = 2a + 8d 6d = a 6d = -4 d = -2/3 term 12 = a + 11d = -4 + 11(-2/3) = -25/3 check: is the 15th term ...

*October 25, 2016*

**Algebra Two**

2500 + .06s ≥ 3100 , where s is his sales .06s ≥ 600 s ≥ 600/.06 s ≥ 10,000

*October 25, 2016*

**Maths GRE**

correct

*October 25, 2016*

**Maths GRE**

correct , so D

*October 25, 2016*

**Math**

fathers age ---- 8x son's age ----- 3x but 8x = 48 x = 6 so the son is 18 or , just using a ratio .... 48/s = 8/3 8s = 144 s = 144/8 =18

*October 25, 2016*

**math**

If PQ = QR , (where P(6,-1), Q(1,3), R(x,8)) √( (3+1)^2 + (1-6)^2) = √( (8-3)^2 + (x-1)^2 ) √41 = √(x^2 - 2x + 26) square both sides 41 = x^2 - 2x + 26 x^2 - 2x - 15 = 0 (x-5)(x+3) = 0 x = 5 or x = -3

*October 25, 2016*

**Math**

average hourly change = (-21 - 63)/12 degrees/hr =

*October 25, 2016*

**maths**

http://www.jiskha.com/display.cgi?id=1477323150

*October 24, 2016*

**maths**

http://www.jiskha.com/display.cgi?id=1477323001

*October 24, 2016*

**maths**

I did this for you when you were Saphina AlMatary http://www.jiskha.com/display.cgi?id=1477322557 I gave you a good hint for the second one Did you even look at it?

*October 24, 2016*

**Math**

good call Steve! (at least I got the right answer, lol)

*October 24, 2016*

**Math**

The largest angle will be opposite the side 28 let it be 2Ø, so each bisected angle is Ø let the bisector form angles A and B along the 28 side, so that A + B = 180° --> B = 180-A and we know sinA = sin(180-A) = sinB let the 28 side be split into x and 28-...

*October 24, 2016*

**maths**

To talk about "roots" you need equations, you don't have any. anyway.... for 3x^2 - 6x - 7 = 0 , the sum of the roots is 6/2 or 3 and the product of the roots is -7/3

*October 24, 2016*

**maths**

check in your text or in your notes what properties are needed to investigate the nature of the roots. hint: it has to do with the determinant. btw. - I can't make your your last equation.

*October 24, 2016*

**Math**

clear case of the cosine law BC^2 = 4^2 + (3√3)^2 - 2(4)(3√3)cos30° carry on

*October 24, 2016*

**maths**

There is no unique or best way to solve these. After doing a few you get a "feel" of what to look for. e.g. for your first one, notice that last one says: y - 4z = 25 , so y = 25+4z - could be useful look at the first two, they both have 1x so lets subtract the 2nd ...

*October 24, 2016*

**Math**

What is your question? What does "and three points at the time of closing" mean?

*October 24, 2016*

**maths**

-did the first one for you - still waiting for your response to the second part of my reply http://www.jiskha.com/display.cgi?id=1477316621

*October 24, 2016*

**Math Check Answers**

both are correct

*October 24, 2016*

**correction- math**

Sara found the area. You want the perimeter = 2(12.75) + 2(8.25) = ..

*October 24, 2016*

**maths**

hard to tell which are your groups of equations.

*October 24, 2016*

**Math Check Answers**

answers: #1 - A #2 - D #3 - B

*October 24, 2016*

**maths**

x^2 - 6x = x^2 - 6x + 9 - 9 = (x-3)^2 - 9 3x^2 + 20x = 3(x^2 + (20/3)x + 100/9 - 100/9 = 3( (x + 10/3)^2 - 100/9 = 3(x+10/3)^2 - 100/3

*October 24, 2016*

**maths**

If the coefficient of x^2 is 1, look for 2 numbers which when multiplied give you the constant, and which when added give you the coefficient of the middle term that is, (-10)(4) = -40 (-10) + 4 = -6 so (x - 10)(x + 4) for the second one: 3x^2 + 20x - 7 = 0 , what method have ...

*October 24, 2016*

**Math**

make a sketch. split the figure into a rectangle and a right-angled triangle. in the triangle the base will be 21-13 or 8 cm and the hypotenuse is 17 let the height be h h^2 + 8^2 = 17^2 h^2 = 225 h = 15 area = rectangle + triangle = 13(15) cm^2 + (1/2)(8)(15) = 255 cm^2

*October 24, 2016*

**math**

to be divisible by 6, it must be divisible by 2 AND 3 8454 is even, so it is divisible by 2 the sum of the digits of 8454 is 21, which is divisible by 3, so 8454 is divisible by 3 (divisibility test for 3: if the sum of the digits of any number is divisible by 3, so is the ...

*October 24, 2016*

**Math**

What is C(4,3) ?

*October 24, 2016*

**Math**

π is indeed an irrational number , but Don Ho said π = 3.14, which is not true, since 3.14 = 314/100 or 157/50 and that would be a rational number all radicals that are not perfect squares, are also irrational number e.g. √5

*October 24, 2016*

**MATH**

You will need brackets in 6/(3-x) = (7-5x)/6 and (3-x)(7-5x) = 36 21 -22x + 5x^2 = 36 5x^2 - 22x - 15 = 0 (x - 5)(5x + 3) = 0 x = 5 or x = -3/5 the common ratio is 6/(3-x) if x =5, common ratio is 6/-2 or -3 if x = -3/5, common ratio is 6/(3 + 3/5) or 5/3

*October 24, 2016*

**maths**

I will assume this is an arithmetic sequence. Let's just use our formulas we know d = 2 sum(10) = 93 ---> n = 10, a = ? (10/2)(2a + 9(2)) = 93 5(2a + 18) = 93 10a + 90 = 93 10a = 3 a = .3 check: 10th term = a+9d = .3 + 18 = 18.3 sum(10) = (10/2)(first + last) = 5(.3+18....

*October 23, 2016*

**maths percentage**

You appear to have a typo ---- 3205% ????

*October 23, 2016*

**maths need help too hard**

4^x+3^x=9^x 4^x+3^x=3^(2x) 4^x = 3^(2x) - 3^x) 4^x = 3^x(3^x - 1 (4/3)^x = 3^x - 1 preliminary check: if x = 1 4+3 = 7 < 9 if x = 2 16 + 9 = 25 < 81 .. if x = 6 4^6 + 3^6 = 4825 < 9^6 for x ≥ 1, the gap between LS and RS is increasing, and RS > LS let's ...

*October 23, 2016*