Friday

May 27, 2016
Total # Posts: 34,808

**MATH - CALC**

f(x) = x^3 - 3x^2 = x^2(x-3) You should be familiar with the general shape of y = 1x^3 + ..... yours crosses at x = 3 and since you have a double root at x = 0, it touches the x-axis at x = 0 find f'(x) and f''(x) , that should be easy when f'(x) is positive, ...
*May 27, 2016*

**math**

really? You are studying the above topic and you are asking this question? Sorry, but .....
*May 26, 2016*

**math**

"first term in an arithmetic sequence is 15" ---> a=15 "the tenth term is 69" ---> a+9d = 69 sub in a = 15 to find d then evaluate a + 3d
*May 26, 2016*

**math**

I will assume d is the diameter. so r = 4, h = 12 V = (1/3)π r^2 h plug in your values
*May 26, 2016*

**Math **

what is 1.35(29.50) ?
*May 26, 2016*

**math**

speed of plane without wind ---- x km/h speed of wind --------- y km/n 5600/(x-y) = 8 700/(x-y) = 1 x-y = 700 ** 9900/(x+y) = 9 1100/(x-y) = 1 x + y = 1100 *** add ** and *** to find x then sub back into **
*May 26, 2016*

**math**

Very very unsafe placement of a ladder.
*May 26, 2016*

**Ratios math**

cars : SUV's = 4:1 = 16:4 SUV's : Minivans = 4:5 now that I have a common "4" for the SUV's in both, I can say cars : SUV's : minivans = 16 : 4 : 5 or = 16x : 4x : 5x but 5x = 20 x = 4 so we have 64 cars, 16 SUV's , and 20 minivans for a total of ...
*May 26, 2016*

**Math**

Kiki, I found the 2.5 seconds for you in your previous post. Just sub that value into your equation. then do it again for t = 4 let me know what you got.
*May 26, 2016*

**Math**

what is C(5,2) x C(3,1) ?
*May 26, 2016*

**Math**

equivalent to finding the vertex of the parabola h = -16t^2 + 80t + 6 the t of the vertex is -b/(2a) = -80/-32 = 2.5 seconds
*May 26, 2016*

**math**

@ sad/jeo 6 almost identical questions without any work shown or indication where your problems are. Steve and I have answered 3 of them. Surely you can do the rest by following our methods.
*May 26, 2016*

**math**

if selling at 600 is a loss of 25%, the cost was .75x = 600 x = 800 so make a profit of 25% on the 800 , he should have sold at 800(1.25) = 1000
*May 26, 2016*

**math**

cost of first = 240/1.2 = 200 cost of 2nd = 240/.8 = 300 percentage change = (200+300)/480 = 1.04166.. he made a profit of appr 4.17%
*May 26, 2016*

**precal**

two numbers: x and y xy = 48 ---> y = 48/x and 1/x + 1/y = 1/3 (x+y)/(xy) = 1/3 (x+y)/48 = 1/3 x+y = 16 x + 48/x = 16 x^2 + 48 = 16x x^2 - 16x + 48 = 0 (x-12)(x-4) = 0 x = 12 or x = 4 if x = 12, y = 48/12 = 4 if x = 4, y = 48/4 = 12 The two numbers are 12 and 4
*May 25, 2016*

**Pre-cal**

cos^2 x = 3/4 cosx = ± √3/2 x = 30°, 150°, 210° or 330° in radians: π/6, 5π/6, 7π/6, 11π/6
*May 25, 2016*

**Math**

Your question is not clear at all. Are we first selecting the committees, then picking the president and vp ? number of committees = C(11,5) = 462 to pick a president , then vice president, order does matter, so 11x10 = 110 or P(11,2) if we are picking the pres and vpres from ...
*May 25, 2016*

**algerba**

the usual way to type a power is to use the ^ to show exponents, e.g. x^2 is "x squared" 0 = −2x^2 − 3x + 8 in standard form is 2x^2 + 3x - 8 = 0 so b^2 - 4ac = 9 - 4(2)(-8) = ...... 4(x + 2)^2 = 36 divide both sides by 4 (x+2)^2 = 9 x+2 = ±√...
*May 25, 2016*

**Math/ ratios/ Fractions/ Singapore Math**

Ross' total --- x Holly's amount = 60-x after spending: Holly has (3/4)(60-x) Ross has x-5 given: Holly/Ross = 1/2 (3/4)(60-x) / (x-5) = 1/2 45 - (3/4)x / (x-5) = 1/2 90 - (3/2)x = x - 5 180 - 3x = 2x - 10 190 = 5x x = 38 take over, using my definitions at the top
*May 25, 2016*

**Math/ more ratios**

let the number of pennies they have be 6x , 5x and 7x respectively 6x + 5x + 7x = 754 18x = 754 x = 41.88.. you are right, it makes no sense, it has to be a whole number. I suspect a typo in the question in your text or whatever your source.
*May 25, 2016*

**correction - College Algebra**

You cannot take log of individual terms, you have to take log of both sides. i.e. log (3^n + 9) = 69 but , why not just do this: 3^n = 60 now log both sides, and use log rules: n log3 = log60 n = log60/log2 = appr 3.727 check: 3^3.727 + 9 = 69.01100 , close enough to 69 if you...
*May 25, 2016*

**math**

amount of her money --- x after spending 2/7 of it, she has (5/7)x left then she spends (2/5) of that, or (2/5)(5/7)x total amount spent = (2/7)x + (10/35)x = (2/7)x + (2/7)x = (4/7)x so (3/7)x = 15 3x = 105 x = 35 <------ money she started with check: she spends (2/7)(35) ...
*May 25, 2016*

**school**

Things you learn from Google: http://www.shmoop.com/walk-two-moons/margaret-cadaver.html Ironic: At the top of the webpage it showed an ad for Plagiarism software
*May 25, 2016*

**math**

his cost price = rs 16 so his selling price should be 1.15(16) or rs 18.4 per dozen. But you want the selling price per hundred so : 18.4/12 = x/100 x = 100(18.4)/12 = 153.333... (notice the fact that he bought 1200 eggs did not enter the calculation) check: cost price per ...
*May 25, 2016*

**Calc-Math**

your derivative is wrong, the xy needs a product rule 2y dy/dt + x dy/dt + y dx/dt - 3dx/dt = 0 plugging in our stuff 2 (-4) + 3(-4) + 1(dx/dt) - 3 dx/dt = 0 -2 dx/dt = 20 dx/dt = -10
*May 24, 2016*

**Calculus**

so your equations can be written as y = 1/√x and y = 1/x^2 let's look at their graphs: http://www.wolframalpha.com/input/?i=plot+y+%3D+1%2F%E2%88%9Ax+,+y+%3D+1%2Fx%5E2 ignore the part for x<0 , since in y = 1/√x, x > 0 so let's take horizontal slices ...
*May 24, 2016*

**Financial Math**

clearly repetition would be allowed in passwords, and I would assume we can start with zero as well number of passwords = (10^3)(26^2) = ...
*May 24, 2016*

**Algebra**

youngest ---- x oldest ---- 2x (2x + 12 + 15 + x)/4 = 13.5 3x + 27 = 54 take over
*May 24, 2016*

**Math**

let the point on the line be (x,y) line is y = (4-x)/4 = 1 - (1/4)x area of rectangle: A = xy = x( 1 - (1/4)x) = x - (1/4)x^2 this is a downwards parabola. We need the vertex the x of the vertex is -b/2a = -1/(-1/2) = 2 then y = 1- (1/4)(2) = 1/2 max area = xy = 2(1/2) = 1 ...
*May 24, 2016*

**Math**

a coefficient is simply the number in front of the variable. So it is -7
*May 24, 2016*

**Algrebra Help!**

just plug in n = 1 n = 2 n = 3 n = 4 and evaluate. e.g. n = 3 value is 3(3-2) - 3 = 3(1) - 3 = 0
*May 24, 2016*

**Math**

let the unit digit be x let the tens digit be y the number is 10y + x 10y + x = 2(y-x) 10y + x = 2y - 2x 8y = -3x mmmmhhhh? do you have a typo?
*May 24, 2016*

**German**

#1 Beantwortest du die Fragen ? - Are you answering the questions ? Fragtest du die Fragen? - Had you asked the questions ? Either one would actually be acceptable, depending which idea you were trying to convey. #2 by the process of elimination, I have to say Wir lernen ü...
*May 24, 2016*

**Algebra**

yup!
*May 24, 2016*

**pre-algebra**

agree
*May 24, 2016*

**geometry**

mmmhhh, did you plot your points? Can you see any way they could form a rectangle?
*May 24, 2016*

**math**

You did not specify whether you want degrees or radians. I will do it for degrees. Repeat for radians, make sure to set your calculator to radians 3sec^2 y = 5(1+tany) We know sec^2 A = 1 + tan^2 A 3(1 + tan^2 y) = 5(1 + tany) 3 + 3tan^2 y = 5 + 5tany 3tan^2 y - 5tany - 2 = 0...
*May 24, 2016*

**math**

#1 cos(x+20) = sin(90 - (x+20) ) , one of the basic rules but sinx = cos(x+20) sinx = sin(70-x) arcsin both sides x = 70-x 2x=70 x = 35 check: LS = sin 35 RS = cos(35+20) = cos 55 but cos 55 = sin 35 so all is good tanx = sinx/cosx = cos(x+20)/cosx = (cosxcos20 - sinxsin20)/...
*May 24, 2016*

**Math**

SA = 2lw + 2 lh + 2 wh plug in ....
*May 24, 2016*

**Maths**

let that time be n years 1.02^n = 2 log both sides, then use rules of logs n log1.02 = log2 n = log2/log1.02 etc
*May 24, 2016*

**algebra**

generally called an inverse proportion ? then ... y = k/x if x = 2 , y = 12 12 = k/2 k = 24 y = 24/x
*May 24, 2016*

**linear-equations-in-one-variable**

or - using one variable, as your title suggests width --- x length --- x+4 new width = x+3 new length = x+7 (x+3)(x+7) - x(x+4) = 81 x^2 + 10x + 21 - x^2 - 4x = 81 6x = 60 etc
*May 24, 2016*

**algebra**

typo, you have no 2nd equation
*May 23, 2016*

**Maths (Need Help)**

(2x-3)^2-3x = 4x^2 - 12x + 9 -3x = 4x^2 - 15x + 9) = (x-3)(4x - 3) (x^2-4)+(x+2)^2 = (x-2)(x+2) + (x+2)(x+2) = (x+2)(x-2 + x+2) = (x+2)(2x)
*May 23, 2016*

**Math**

prob =(1/4)(1/2) = 1/8
*May 23, 2016*

**Math**

#1 you have 4 colours and 2 ways to flip a coin so there should be 8 possible outcomes. your choice has only 6 outcomes #2, correct #3, correct #4, no, there are 21 students, 12 of which are boys prob = 12/21 = 4/7 you stated the ratio of girls : boys
*May 23, 2016*

**Maths**

I bet you mean: 4/(a^2 -2a-3) + a/(a-3) + a/(a+1) = 4/( (a-3)(a+1) + a/(a-3) + a/(a+1) = ( 4 + a(a+1) + a(a-3) )/( (a-3)(a+1) ) = (2a^2 - 2a + 4)/( (a-3)(a+1) ) or = 2(a^2 - a + 2)/( a^2 - 2a - 3)
*May 23, 2016*

**Math**

in 22 23 24 25 26 <--- the x's out12 16 20 24 28 <--- the y's did you notice that for every increase of 1 in your x, the y increases by 4 ? so we have y = 4x + b plug in (22,12) 12 = 4(22) + b b = -76 rule: y = 4x - 76 test it for some of the given values, it ...
*May 23, 2016*

**Math**

factor it cosx(1 + 2sinx) = 0 cosx = 0 or sinx = -1/2 if cosx = 0 x = π/2 , 3π/2 for sinx = -1/2, we know x is in III or IV we also know that sin π/6 = + 1/2 x = π + π/6 or 7π/6 x = 2π - π/6 = 11π/6 so you had 2 of the 4 answers
*May 23, 2016*

**Math**

Whatever happened to the ol' fashioned way: 2/6 = 1/3 So 1/3 of the 12 kids are girls , and (1/3(12) = 4 so, ........ (drum roll) 4 of the 12 kids were girls.
*May 23, 2016*

**Math**

let the food needed each day per soldier be x units total food available = 1200(28)x = 33600x after 4 days, 6/7 of the amount would be left or (6/7)(1200)(28)x = 28800x let the number of soldiers who left be n so (1200 - n)(x)(38) = 28800x (1200-n)(38) = 28800 45600 - 38n = ...
*May 23, 2016*

**Maths**

Now: daughter --- x mom ------- 3x 5 years from now: daughter = x+5 mom = 3x+5 3x+5 = 2.5(x+5) take over
*May 23, 2016*

**math**

each of the equal angles ---- x third angle ---- 2x - 16 x + x + 2x-16 = 180 take over
*May 23, 2016*

**elective maths**

volume would be proportional to the cube of the radius so original radius =(1.06)^(1/3) But area is proportional to the square of the radius so new area = ( (1.06)^(1/3) )^2 = 1.06^(2/3) = 1.0396 so the surface area increased by appr 3.96%
*May 23, 2016*

**UNISA**

2y - 5x - 1 = 0 better form: 5x - 2y + 1 = 0 since your new line is parallel to the above, it would differ only in the constant, since it must have the same slope new line: 5x - 2y + c = 0 but the point (2, 1/4) lies on it, so 10 - 1/2 + c = 0 c = -19/2 5x - 2y - 19/2 = 0 or ...
*May 23, 2016*

**Math**

amplitude is 25 let's use a sine curve function and let's start with h = 25sin kt we want the period to be 7 2π/k = 7 k = 2π/7 so h = 25 sin 2π/7 t the max of that curve is 25 but we want it to be 100 so we have to raise our function by 75 h = 25 sin 2&#...
*May 23, 2016*

**Math**

assuming the 2 can be of any suit prob(your event) = (4 + 1)/52 = 5/52 if both the 2 and the 7 have to be diamonds, then prob = 2/52
*May 22, 2016*

**Math**

grandma's age --- 10x + y mother's age ---- 10y + x one year ago: grandma : 10x+y - 1 mothers: 10y+x - 1 10x+y - 1 = 2(10y+x-1) 10x + y - 1 = 20y + 2x - 2 8x - 19y = -1 8x = 19y-1 x = (19y-1)/8 try different y's so that the numerator is a multiple of 8 e.g. when y...
*May 22, 2016*

**Pre-Calc**

Prob(3 or 4 are aces) = ( C(4,3)C(48,2) + C(4,4)C(48,1) )/ C(52,5) = ....
*May 22, 2016*

**Math**

Each pear costs $4 more than each Apple --- p = a + 4 Now , that's some expensive fruit !! 6a = 4p 6a = 4(a+4) 6a = 4a + 16 2a = 16 a = 8 , then p = 12 An apple costs $4 and a pear costs $12 WOW, but the answers check out for you info
*May 22, 2016*

**Math**

What is 4000(1.01025)^60 ?
*May 22, 2016*

**algebra**

Trying to make sense out of the gibberish English. I will assume you meant: How old will her daughter be when her age is 1/3 of her mother's age. daughter now : ---- 0 mother now -------21 0+x = (1/4)(21+x) 4x = 21 + x 3x = 21 x = 7 Find their ages in 7 years, and see if ...
*May 22, 2016*

**Math**

original numbers: x and y original product : xy new numbers: .75x and .5y new product = .375xy or (3/8)xy change in product = (5/8)xy percentage change = (5/8)xy/(xy) = 5/8 = .625 = 62.5 %
*May 22, 2016*

**Maths**

(3/4)x + (1/7)x + 27 = x times 28 21x + 4x + 756 = 28x at this point I can tell that he spent 25/28 of his money and he would have 3/28 of it left over 25x + 756 = 28x 3x = 756 x = 252 state you conclusions
*May 22, 2016*

**MATHS**

wouldn't that have to be 76479 ?
*May 22, 2016*

**Pre-Calc**

Prob(3 hearts) = C(13,3)/C(52,3) = 286/22100 = .0129 yes
*May 22, 2016*

**maths**

clock #1 runs at (29/30)t relative to real time clock #2 runs at (61/60)t relative to real time (61/60)t - (29/30)t = 10 times 60 61t - 58t = 600 3t = 600 t = 200 minutes or 3hours, and 20 minutes which would make it 9:30 am
*May 22, 2016*

**Mathematics**

(...7)(...7) ends in 9 (.....9)( .... 7) ends in 3
*May 22, 2016*

**Math**

Aaron ---- x his dad --- 9x One year ago: Aaron --- x-1 his dad --- 9x-1 9x-1 = 11(x-1) + 2 9x - 1 = 11x - 11 + 2 8 = 2x x = 4 Aaron is 4 dad is 36 one year ago Aaron -- 3 dad ---- 35 ---> was he 2 more than 11 times 3 ?? YES
*May 22, 2016*

**Math**

monthly rate = .0585/12 = .004875 outstanding balance = 22350(1.075) - 1200 = 22826.25 interest for 1st month = 22826.25(.004875) = 111.28 amount going to principal = 475.25 - 111.28 = $363.97
*May 21, 2016*

**math**

first piece ---- x 2nd piece ---- 12-x I will assume the second piece is 3/2 inches longer than the first piece 12-x - x = 3/2 12-2x = 3/2 24-4x = 6 4x = 18 x = 4.5 first piece is 4.5 2nd piece = 12-4.5 = 7.5 So, what do you think?
*May 21, 2016*

**Addition to .. - logarithm math-need help!!!!**

My equation near the end should have included: 5 log 4 x + 48log x 4 = x/8 5 log4 x + 48/log4 x = x/2 or 5log 4/log x + 48log x/log 4 = x/2 btw, that is what I used in Wolfram , so my answer stands as is
*May 21, 2016*

**logarithm math-need help!!!!**

5logxbase4+48log4basex=x/8 ---> 5 log 4 x + 48log x 4 = x/8 One of rules of logs: log a b = 1/log b a and furthermore: log a b = log b/log a so 5 log 4 x + 48log x 4 = x/8 I don't know of any nice method to solve this, I ran it through Wolfram and got x = 2130.13 , ...
*May 21, 2016*

**Math**

This same question was recently in the news http://www.iflscience.com/editors-blog/can-you-solve-math-problem-went-viral-japan the way it was written by Jerry the answer would be 9
*May 21, 2016*

**Algebra**

Since you are putting the marble back, the prob of the second event is the same as the first one. Prob(red,red) = (2/10(2/10) = 1/25
*May 20, 2016*

**math**

What is the meaning of the "x" between the two equations? is the second equation 3y = 13 ? Then y = 13/3, which does not show up in any of your choices.
*May 20, 2016*

**HELP ON MATHHHH!!!!**

I think you want something like 3x - 4 ≤ 15 then 3x ≤ 19 x ≤ 19/3 If this is what you meant then the values from your set that would work are: { 0, 3, 5, 6} Make suitable adjustments to my my solution of you meant something other than ≤
*May 20, 2016*

**Math Help!**

#1, correct #2. Volume of any solid that comes to a point: V = (1/3) base x height = (1/3)(24^2)(24) = 1/3(24^3 = 4608
*May 20, 2016*

**nawal**

You should make a point to memorize the ratio of sides of the 30-60-90° triangle, which is 1 : √3 : 2 so for yours: √3/1 = √6/x √3x = √6 x = √2 then the hypotenuse = 2√2 area = (1/2)base x height =(1/2)(√2)(√6) = (1/2...
*May 20, 2016*

**math**

Just set up a simple ratio: 60/1.5 = 100/t
*May 20, 2016*

**math**

nothing found in the coefficients. for the m's --- > m^6 for the n's ----> n so GCF = m^6 n
*May 19, 2016*

**Math Trigonometry**

I made a sketch with Chicago as C, A as the end of the first flight, and B as the end of the 2nd flight. In triangle ABC AC = x, AB = 150, BC = 195, angle A = 65° by the sine law: sinC/150 = sin 65/195 sinC = .69715... C = 44.199... (I stored that in calculator's ...
*May 19, 2016*

**math**

Did you not read Steve's answer to your previous question regarding the condition to have a triangle? http://www.jiskha.com/display.cgi?id=1463702386
*May 19, 2016*

**Algebra**

number of .15 increases ----- n price per bushel = 5 + .15n number of bushels sold = 1000 - 10n income = (5+.15n)(1000 - 10n)
*May 19, 2016*

**math**

yes
*May 19, 2016*

**math**

let each of the straights be x m then the perimeter is 2x + 2half-circles = 2x + circumference of 1 circle 2x + 2π(35) = 400 solve for x
*May 19, 2016*

**College Algebra**

pounds of $8 nuts ----- x pounds of other nuts ---- 41-x 8x + 2(41-x) = 7(41) solve for x
*May 19, 2016*

**Math**

2^x=17 take log of both sides, then use log rules x log2 = log 17 x = log17/log2 = appr 4.087 4log4^(x)=7 log 4^x = 1.75 4^x = 10^1.75 4^x = 56.23413... repeat the same steps I used in the first one to finish it
*May 19, 2016*

**Algebra 2**

find the z-score for 140, then use your tables or charts or some software to find that .1587 will pass so number of the 360 that will pass = .1587(360) = 57 rounded to the nearest person
*May 19, 2016*

**Trig**

If sinØ = 3/7, y=3 , r = 7 and x^2 + 3^2 = 7^2 x = ± √40 Ø could be in I or II if Ø is in I sinØ = 3/7 cosØ = √40/7 cos(π/2 - Ø) = cos π/2 cosØ + sin π/2 sinØ = 0 + sinØ = 3/7 If &...
*May 19, 2016*

**Algebra**

y = -2/5x + 3 multiply each term by 5 , the LCD 5y = -2x + 15 get the x's and y's to one side, the constant to the other 2x + 5y = 15 None of your choices are correct. e.g. for y = (-2/5)x + 3 , (the original) the y-intercept is (0,3) (0,3) does not satisfy any of the ...
*May 19, 2016*

**math**

Assuming the 2 bags are distinguishable. then : C(5,1)xC(4,4) + C(5,2)xC(3,3) + C(5,3)xC(2,2) + C(5,4)xC(1,1) = 5 + 10 + 10 + 5 = 30 notice that this is row 1 5 10 10 5 1 of Pascal's triangle with out the leading and ending 1's. If the 2 bags are indistinguishable, ...
*May 19, 2016*

**algebra 1**

You want to find: −16t^2 + 90t + 50 = 28 + 48.8t 16t^2 -41.2t - 22 = 0 by the formula: t = (41.2 ± √3105.44)/32 = appr 3.03 or -.454 so you are correct, it is between 3 and 4, much closer to 3 seconds
*May 19, 2016*

**Math**

Flaw in problem: Two persons mentioned, but 3 terms in the ratio
*May 19, 2016*

**Calculus**

The way you worded the question, "How quickly is it moving away from the observer at that moment" , implies to find the rate at which the distance between the balloon and the observer changes. So we could just use Pythagoras after t sec, height of balloon is 8t ft so...
*May 18, 2016*

**Algebra 2**

I have to know more about the spinner. How many colours, etc
*May 18, 2016*

**Algebra**

nope, it is 4 units up Make a table of values of each using the same x's and see what happens http://www.wolframalpha.com/input/?i=plot+y%3D+-6+x%5E2+%2B4+,+y%3D+-6x%5E2
*May 18, 2016*

**alg 2**

the centre of (x - 2)^2 + (y + 1)^2 = 16 is (2,-1) Now move that centre 4 units to the left and 6 units up New centre is ....... new equation is .......
*May 18, 2016*

**Calculus**

a = 1.1+2(t^1/2) v = 1.1t + (2/(3/2)) t^(3/2) + c v = 1.1t + (4/3)t^(3/2) + c when t = 0 , v = 0 0 = 0 + 0 + c -----> c = 0 v = 1.1t + (4/3) t^(3/2) when t = 9 v = 1.1(9) + (4/3) (9)^(3/2) = 9.9 + (4/3)(27) = 9.9 +36 = 45.9 m/h
*May 18, 2016*