Tuesday

September 30, 2014

September 30, 2014

Total # Posts: 27,190

**precal**

or , using the standard a to be first term, r the common ratio ar^12 = -72 ar^9 =9 divide them r^3 = -8 r = -2 , then from ar^9 = 9 a = 9/(-2)^9 = -9/512 term(7) = ar^6 = (-9/512)(-2^6) = -576/512 = -9/8
*September 30, 2014*

**Math Gr.12**

Finding the vertex would give you the answer what method have you learned to find the vertex?
*September 30, 2014*

**Pre-Cal**

According to the directions Average cost = (300+5x)/x
*September 30, 2014*

**College Prep Math 4**

2√(5x) = 100 √(5x) = 50 square both sides 5x = 2500 x = 500
*September 30, 2014*

**Math Gr 12**

h = -4.9t^2 + 29.4t for the initial height, t = 0 , so h = 0 "reach the ground" implies h = 0 -4.9t^2 + 29.4t = 0 t(-4.9t + 29.4) = 0 so t = 0 ----> the initial time and height or t = 29.4/4.9 = 6 so it will return to the ground after 6 seconds
*September 30, 2014*

**math- pre calc/trig**

Bosnian is simply using the Pythagorean Theorem , where he called each of the sides a and the diagonal d d^2 = a^2 + a^2 2a^2 = d^2 2a^2 = (7√2)^2 = 98 a^2 = 49 a = 7
*September 30, 2014*

**college algebra**

nice parabola, what about it ?
*September 29, 2014*

**Math**

1. did you mean 4/(3 + √5) or 4/3 + √5 , the way you wrote it. secondly, what do you want to "solve" ? are you studying rationalizing the denominator? My question also applies to the other two questions
*September 29, 2014*

**Math**

clearly 4y(y^2+1)(2y^2+1) Always check your factored answer by expanding it again to make sure the original comes back
*September 29, 2014*

**Math**

looks like a common factor of 4y can you finish it?
*September 29, 2014*

**Precalculus**

First of all , let me point out a discrepancy in the wording of your question The way your equation is written as y = x^2 + 9x - 36 it should have asked for the x-intercepts of the function To do that , we realize that for an x-intercept, the value of y = 0 so your function ...
*September 29, 2014*

**Math**

your number is 2*3*5*7 = 210 Now for factors take any combination of single factors --- 4 of them pairs of factors -- you should find 6 of them triples of factors --- you should find 4 of them all of them ---- clearly the number 210 itself
*September 29, 2014*

**algebra**

write it this way: (1+x)/(1+x^2) = 2/5 cross-multiply 2 + 2x^2 = 5 + 5x 2x^2 - 5x - 3 = 0 (x - 3)(2x + 1) = 0 x = 3 or x = -1/2
*September 29, 2014*

**Math**

done when you posted under a different name, why did you switch names ? http://www.jiskha.com/display.cgi?id=1412031500
*September 29, 2014*

**Calculus**

e^-x √(3e^(2x) - 5/4) = e^x multiply both sides by e^x √(3e^(2x) - 5/4) = e^2x square both sides 3e^(2x) - 5/4 = e^4x times 4 12 e^2x - 5 = 4e^4x 4e^4x - 12 e^2x + 5 = 0 (2e^2x - 1)(2e^2x - 5) = 0 e^2x = 1/2 OR e^2x = 5/2 if e^2x = 1/2 ln both sides 2x lne = ln1 - ...
*September 29, 2014*

**Math**

Each "pair" of factors allows a rectangular arrangement so which number has more factor pairs, 75 or 60 ? e.g. factor pairs of 75 1 75 3 25 5 15 and 60 ?
*September 29, 2014*

**math**

let's intersect them: -x^2 - 3x + 6 = 3x + k -x^2 - 6x + 6-k = 0 x^2 + 6x + k-6 = 0 to have 2 distinct real solutions , the discriminant must be > 0 b^2 - 4ac > 0 36 - 4(1)(k-6) > 0 36 -4k + 24 > 0 > 0 -4k > -60 k < 15 Notice in my graph, when k = 0, ...
*September 29, 2014*

**Algebra**

cost = 65 + 75t so if 65+75t = 196.25 75t = 131.25 t = 1.75 so the job took 1 hour and 45 minutes, I will let you figure out when the job was done
*September 29, 2014*

**AP Calc B/C**

Wolfram says: http://integrals.wolfram.com/index.jsp?expr=e%5Ex%2F%281+-+e%5E%282x%29%29%5E%283%2F2%29&random=false
*September 29, 2014*

**Algebra**

Go with PsyDAG's solution, I hit the 3 key instead of the 2
*September 29, 2014*

**Algebra**

number of marbles in each bag --- x 3x + 3 = 29 3x=27 x=9 each bag has 9 marbles
*September 29, 2014*

**Pre-Calculus/Trignometry**

yes, good job
*September 29, 2014*

**Pre-Calculus/Trignometry**

Not totally familiar with the terminology of [2, infinity] , don't know if the 2 is included or not If the 2 in included, how about f(x) = √(x-2) if the 2 is excluded, we would use something like f(x) = 5/√(x-2)
*September 29, 2014*

**math**

number of dimes --- x number of quarters -- x-25 10x + 25(x-25) = 1650 10x + 25x - 625 = 1650 35x = 2275 x = 65 So 65 dimes and 40 quarters. check: 65 dimes = $6.50 40 quarters = $10 total = 16.50
*September 29, 2014*

**Math Help**

you have to learn to recognize the patterns. It looks like the primary function is 4/(something)^2 so let f(x) = 4/x^2 Now I see that instead of x in the denominator , I see 5x+2 so I let g(x) = 5x+2 so f(x) = 4/x^2 and g(x) = 5x+2 check: suppose we find f(g(x)) = f(5x+2) = 4...
*September 29, 2014*

**math**

So you were financing $5500 for 48 months with a monthly payment of $165.51 let the monthly interest rate be i 165.51( 1 - (1+i)^-48 )/i = 5500 This type of equation is very difficult to solve. In the "olden days" we used methods such as interpolation to get ...
*September 29, 2014*

**Algebra**

5x^3 . 2x^2 - 10x^4 + 3x^5 + 3x .(-2)x^4 = 10x^5 - 10x^4 + 3x^5 - 6x^5 = 7x^5 - 10x^4 The word "solve" is usually used when dealing with equations, that is, we solve an equation. You did not have an equation, so the instructions would be to "simplify" the ...
*September 28, 2014*

**Calculus**

change y = 2^x to ln y = x ln2 now take derivative: dy/dx / y = ln 2 dy/dx = y ln2 = ln2 (2^x)
*September 28, 2014*

**math**

number of children --- c number of adults ---- 155-c 5.3c + 8.7(155-c) = 1137.7 5.3c + 1348.5 - 8.7c = 1137.7 -3.4c = -210.8 c = 62 So 62 children tickets were sold on Friday
*September 28, 2014*

**algebra 1 question**

you can't just write things down . I hope nobody showed you how to solve equations that way. remember, "whatever you do to one side of the equation you must do to the other 3/2 x - 4 = 16 Add 4 to both sides 3/2 x = 20 multiply both sides by 2 3x = 40 now divide both ...
*September 28, 2014*

**Math quick question!**

12a^2-5a-2m^2 = (3a -2m)(4a + m) If we add 1 m to the end of each length and width area of garden including path = (3a-2m+2)(4a+m+2) So area of path = (3a-2m+2)(4a+m+2) - (3a -2m)(4a + m) I will let you do the expanding and simplifying sub in a = 6 into your answer for the ...
*September 28, 2014*

**pre algebra**

let the radius be r 2πr = 16π r = 8 so the height is 4 inches and the radius is 8 inches. SA = 2 circles + a rectangle = 2πr^2 + 2πrh = 2π(8)^2 + 2π(8)(4) = ....
*September 28, 2014*

**Calculus Maxima/Minima**

Let the time passed since the truck went through the intersection be t seconds Make a diagram Let the distance between them be D ft I see that D^2 = (40t)^2 + (120-30t)^2 = 1600t^2 + 14400 - 720t + 900t^2 = 2500t^2 - 7200t + 14400 2D dD/dt = 5000t -7200 but at a minimum of D...
*September 28, 2014*

**trigo**

use cos 2A = 1 - sin^2 A or cos t = 1 - 2sin^2 (t/2) 2sin^2 (t/2) = 1 - 1/3 = 2/3 sin^2 (t/2) = 1/3 sin (t/2) = 1/√3 , since you want quadrant I, we use only the positive result
*September 28, 2014*

**trigo**

after doing what ?
*September 28, 2014*

**Math Homework**

1. keep in mind that both f(x) and g(x) would be undefined for x=0 so even though g/f = (1/x) / (1/x^2) = x the final function would still be undefined (actually it would be indeterminate) for x = 0 so the domain is : set of all real numbers, x ≠ 0
*September 28, 2014*

**Pre-Calculus**

How did you get -3 ? (f-g)(x) = 4 - (2x-1) = 4 - 2x + 1 = -2x + 5
*September 28, 2014*

**Pre-Calculus**

if f(x) = 2x-5 and g(x) = 4 then (f-g)(x) = 2x-5 - 4 = 2x - 9 Do #2 in the same way
*September 28, 2014*

**geometry**

Don't you just have a nice right-angled triangle? You should recognize 5-12-13 as one of the common ones with integer lengths, if not AC^2 = 5^2 + 12^2 = 169 AC = √169 = 13
*September 28, 2014*

**Fractions**

1. area of each piece = 8.5(11) = 93.5 inches^2 2. no definite answer since we don't know the dimensions of the larger piece. e.g. it could be 20 by 50, or 25 by 40 , or 16 by 62.5, or .....
*September 28, 2014*

**math**

Using the simple interest formula I = PRT 6 = 100(R)(2/52) R = 6(52)/200 = 1.56 or 156 % per year (in the Middle Ages, they would have been burned at the stake for usury)
*September 28, 2014*

**math**

let the side of the smaller square be x let the side of the larger square be y 4x/4y = 1/5 x/y = 1/5 y = 5x area of larger = 250 y^2 = 250 y = √250 = 5√10 then 5x = 5√10 x = √10 perimeter = 4x + 4y = 4√10 + 20√10 = 24√10 or appr 75.9 m
*September 28, 2014*

**Geometry**

This is a more difficult problem than it first appears. Here is a complete solution to your problem using a radius of 10 Change the appropriate numbers to suit your solution http://www.analyzemath.com/Geometry/circles_problems.html
*September 28, 2014*

**Pre-Calc**

f(x) = 3x^2 + 2x + 4 whatever replaces x, replace it in the algebraic expression f(♠) = 3♠^2 + 2♠ + 4 f(☂) = 3☂^2 + 2☂ + 4 f(2) = 3(2)^2 + 2(2) + 4 = 20 follow the same pattern: f(a+h) = 3(a+h)^2 + 2(a+h) + 4 = 3(a^2 + 2ah + h^2) + 2a + 2h...
*September 27, 2014*

**quanta tive skills and reasoning**

N(math) + N(psych) - N(math AND psych) = N(math OR psych) 140+85-65 = N(math OR psych) = 160 (the 250 did not enter the picture unless you want to note that 90 took neither math nor psych )
*September 27, 2014*

**Math plz help.**

1, correct 2. correct 3. F 4. B 5. A 6. C
*September 27, 2014*

**Algebra**

number of ounces of $1 stuff --- x 4(40) + 1(x) = 2.2(40+x) solve for x, you should get x = 60
*September 27, 2014*

**Pre-Calc**

Wow , that would be overkill, but anyway .... first of all , it is very difficult to write it in matrix form in this format, so you would have the matrix 3 2 2-4 multiplied by the column matrix x y = 14 4 I will assume you know how to find the inverse of a 2by2 matrix, and how...
*September 27, 2014*

**Pre-Calc**

I would double the first then add that to the 2nd to get 8x = 32 x =4 sub into the first: 12 + 2y = 14 2y = 2 y = 1 x=4, y =1 check by subbing those values into both equations, they should work
*September 27, 2014*

**Calculus**

the whole problem becomes trivial when you realize that (0,0) does not lie on y = lnx If you recall your properties and definition of logs, you know that we can only take logs of positive numbers, that is, ln (0) is undefined. Your method is correct until you come to the point...
*September 27, 2014*

**Math. I have a question.**

2l+2w=800 l+w=400 so he can build an infinite number of such rectangles as long as the length + width = 400 e.g. 1 by 399 2 by 398 3 by 397 ... .1 by 399.9 .01 by 399.99 etc if you allow sides with non-integer values.
*September 27, 2014*

**algebra**

shortest side --- x each of the other sides --- 3x x + 3x + 3x = 126 7x = 126 carry on ....
*September 26, 2014*

**algebra**

amount of $8 coffee --- x amount of $ 4 coffee -- 60-x 8x + 4(60-x) = 5.25(60) 8x + 240 - 4x = 315 4x = 75 x = 18.75 lbs
*September 26, 2014*

**Trigonometry**

8% = 8/100 = .08 so tanØ = .08 Ø = 4.57 = 4.6° to the nearest tenth
*September 26, 2014*

**math**

You don't define what your x is, so your equation makes no sense to me. The left side of your equation has units of distance, while your right side is speed, thus it is gibberish. If x is the time needed the distance covered by the slower car = 15 + 50x the distance ...
*September 25, 2014*

**Math URGENT QUICK QUESTION**

9-6x-3x^2 notice the common factor of -3 = -3(x^2 + 2x - 3) = -3(x + 3)(x - 1) x^2 - 8x + k If we have 1x^2 at the front, then the sum of the roots equal the coefficients of the middle term, and the product of the constants. so x^2 - 8x +7 ?? two numbers that have a sum of -8 ...
*September 25, 2014*

**calculus 1**

According to your answer of a positive dy/dt, the laddder would be sliding UP the wall. Since the ladder is sliding away from the wall along he ground, dx/dt should be +4 ft/sec which would make dy/dt = -3 ft/sec, showing that y is decreasing, thus sliding DOWN the wall as ...
*September 25, 2014*

**algebra**

let the distance be x nautical miles x/12 + x/10 = 8.8 times 60 5x + 6x = 528 x = 48 n miles. check: one way = 48/12 = 4 hrs other way = 48/10 = 4.8 , for a total of 8.8 hrs
*September 25, 2014*

**Calculus I**

A function is even if f(-a) = f(a) a function is odd if f(-a) = -f(a) f(a) = a^3(a^3) + a^3 = a^3(a^3 + 1) f(-a) = -(a^3)(a^3) - a^3 = - (a^3)(a^3 + 1) notice that abs(a^3) is always positive So what do you think? You might try it with numbers, e.g. f(2) = 8(8) + 8 = 72 f(-2...
*September 23, 2014*

**Algebra**

Let the amount of the 4.50 coffee be x lbs 7.5(20) + 4.5x = 5(20+x) solve for x
*September 22, 2014*

**math**

questions in 2nd test --- x so 48/x = (1/2)(24/25) 48/x = 24/50 24x = 2400 x = 100 There were 100 problems check: 1st test = 24/25 = 96% 2nd test = 48/100 = 48% , which is 1/2 of 96%
*September 18, 2014*

**Algebra 2**

use brackets please (x/4 - 4/x) / (1 - 4/x) = (x/4 - 4/x) / (1 - 4/x) * (4x)/(4x) , actually multiply by 1 =(x^2 - 16)/(4x-16) = (x+4)(x-4)/(4(x-4)) = (x+4)/4 , x ≠ 4
*September 18, 2014*

**Algebra 2**

(5√7)/(√6) = (5√7)/(√6) * √6/√6 = 5√42/6 A good idea is to check your answer with your calculator evaluate the original, then evaluate your simplified answer, you MUST get the same answer.
*September 18, 2014*

**math**

let the original fraction be a/b equation #1: (a - 3)/b = 1/2 b = 2a - 6 equation #2: (a+5)/(b+7) = 3/4 4a + 20 = 3b + 21 4a - 3b = 1 sub in #1 4a - 3(2a-6) = 1 4a-6a+18 = 1 -2a = -17 a = 17/2 b = 2(17/2)-6 = 11 our fraction is (17/2)/11 = 17/22 When we check with 17/22, we ...
*September 18, 2014*

**science/math**

your numeral answer is correct (actually -7/3) As I noted in an earlier post, since it asks for the skater's "acceleration" and he slows down to a stop , your answer should be expressed as a negative so a = -2.3
*September 18, 2014*

**science/math**

I get 2.571 , which would be 2.6 correct to one decimal place
*September 18, 2014*

**science/math**

correct, assuming the runner starts from rest your answer should be in m/s^2
*September 18, 2014*

**science/math**

your of acceleration should be 8 m/s^2 your answer is correct
*September 18, 2014*

**Math**

did you mean y = -.25x + 5 ? several ways to do this, here is a way that is simple to understand Let's take two points on the line x = 0, y = 5 ---> (0,5) x = 4, y = 4 ---> (4,4) when we reflect across the x-axis, the x values stays the same, but the way values ...
*September 18, 2014*

**science/math**

Here is my mathematical approach physics has nice formulas for this v = at + c when t = 0, v = 25 so 25 = 0+c c = 25 then v = at + 25 when t = 10 , v = 6 6 = 10a + 25 10a = -19 a = -1.9 Whenever you see the word deceleration (things slow down) you can expect a negative result...
*September 18, 2014*

**Algebra1**

divide by -3 |2x+6| = 4 so 2x+6 = 4 OR -2x -6 = 4 ---> 2x = -2 , x = -1 or ---> -2x = 10 , x = -5
*September 17, 2014*

**math**

speed of plane --- x speed of wind ---- y 3927/(x+y ) = 7 ---> 7x + 7y = 3927 3437/(x-y) = 7 ----> 7x - 7y = 3437 add them 14x = 7364 x = 526 then but subbing in x - 526 into either equation y = 34
*September 17, 2014*

**Analytic Geometry**

divide by 9 x^2/(1/9) + y^2 = 1 a^2 = 1/9, a = ±1/3 b = ±1 so we have an ellipse with the major axis as the y-axis vertices: on x-axis ( 1/3,0) , (-1/3 , 0) on y-axis (0,1) , (0,-1) foci: c^2 + (1/3)^2 = 1^1 c^2 = 1-1/9 = 8/9 c= ± (2√2)/3 this will ...
*September 17, 2014*

**Linear Algebra**

t1(1,1) + t2(1,-1) = (13,-12) (t1,t1) + (t2,-t2) = (13,-12) (t1+t2 , t1 -t2) = (12, -12) so t1+t2 = 13 t1-t2 = -12 add them 2t1 = 1 t1 = 1/2 subtract them 2t2 = 25 t2 = 25/2 b) using he results of above replace 13 with x1 and -12 with x2 and repeat my steps
*September 17, 2014*

**Algebra 1**

4x^2 - 1 It is essential that you recognize and memorize the difference of squares pattern for your factoring skills
*September 17, 2014*

**math**

let the shortest be x inches let the longest piece be x+39 let the other piece be (1/2)(x+39) x + x+39 + (1/2)(x+39) = 132 don't like fractions, so multiply everybody be 2 2x + 2x + 78 + x+39 = 264 5x = 147 x = 29.4 inches shortest is 29.4 inches longest is 68.4 inches ...
*September 17, 2014*

**Pre-Calculus**

3 strikes ... 1. slope AB = (2-0)/(-2-3) = -2/5 slope CD = (4+1)/(-1+3) = 5/2 So perpendicular 2. slope AB = (1+3)/(1-4) = -4/3 slope CD = (1+3)/(2-5) = -4/3 so parallel 3. slope EG = (2-0)/(-3-2) = -2/5 so slope of perpendicular is 5/2 Looks like somebody has some serious ...
*September 14, 2014*

**ccs trigo**

info missing
*September 14, 2014*

**Math**

looks like Damon lost about $10,000 interest should have been $9,998.80
*September 13, 2014*

**maths**

I disagree with your reasoning. I read it that she spent 2/5 of her pocket money on a necklace so she spent 6 on a necklace So far she has spent 5 + 6 or 11 leaving her with £ 4 or 1/3 + 2/5 = 11/15 leaving 4/15 (4/15)(15) = 4
*September 13, 2014*

**Math**

looks like y = x^3 for x < 0 , y = -x^3 for x ≥ 0 to me
*September 12, 2014*

**Pre-Calculus**

I agree with your choices
*September 12, 2014*

**Algebra 3-4**

time of burn of 2nd stage = x seconds time of burn of 1st stage = x+28 x + x+28=152 2x = 124 x = 62 2nd stage takes 62 seconds 1st stage is x+28 = 62+28 = 96 sec
*September 12, 2014*

**Algebra**

Sam, did you not see Steve's reply? why not try some values? e.g. let a = 4, b = 5 then 2ab= 2(4)(5) = 40 a^2 + b^2 = 16 + 25 = 41 so what do you think?
*September 12, 2014*

**Algebra**

let's assume that the silo will be totally filled including the hemisphere. radius of cylinder and hemisphere is 15 let the height up to the hemisphere be h ft πr^2 h + (1/2) (4/3)πr^3 = volume π(15)^2 h + (2/3)π (15)^3 = 10800 225πh + 2250π...
*September 12, 2014*

**College Algebra**

rate of current --- x mph let the distance each way by y miles so upstream distance: y = (24/60)(5-x) downstream distance y = (16/60)(5+x) but they are both equal to y, so 24(5-x)/60 = 16(5+x)/60 times 60 24(5-x) = 16(5+x) 120 - 24x = 80 + 16x -40x = -40 x = 1 So the current ...
*September 12, 2014*

**Algebra 1**

amount of 10% solution ---- x L amount of 60% solution ---- 200-x L .1x + .6(200-x) = .5(200) times 10 x + 6(200-x) = 5(200) x + 1200 - 6x = 1000 -5x = -200 x = 40 check: .1(40) + .6(160) = 4+96 = 100 which is 50% of 200L
*September 12, 2014*

**math**

2=1(1+.127/2)^2t , where t is half-years (2t is years) 2 = (1+.127/2)^2t log2=log (1+.127/2)^2t by the rules of logs ... log2=2t log(1+.127/2) 2t = log2/log(1.0635) 2t = 11.26 So it would take about 11 1/4 years or 11 years and 3 months
*September 11, 2014*

**math**

The amount of salt stays the same .20(110-x) = .12x times 100 20(110-x) = 12x 2200 - 20x = 12x 2200 = 32x x = 68.75
*September 11, 2014*

**math**

distance to island --- n miles x/11 + x/10 = 4.2 times 110 10x + 11x = 462 x = 22 nautical miles
*September 11, 2014*

**math**

I suspect a typo
*September 11, 2014*

**math**

done, look for your other post
*September 11, 2014*

**math**

done, look for you other post
*September 11, 2014*

**Trig**

Make your sketch, label the person nearest the obelisk as A and the person's position as B Top of obelisk as P and its bottom as Q. Look at triangle PAB angle B = 44 angle PAB = 180-65 = 115 then angle APB = 21 by the sine law: AP/sin44 = 25/sin21 AP = 25sin44/sin21 In the...
*September 10, 2014*

**math**

400 m in 1min, 32 sec = 92 seconds so 100 m in 92/4 or 23 seconds you did not specify what rate we are talking about m/s or s/m or ...
*September 10, 2014*

**Math**

Using trig: let the speed be x km/h after making your diagram, x^2 = 10^2+3^2 - 2(10)(3)cos 135° = 151.426... x = 12.3 km/h angle: using the sine law: sinØ/3 =sin135/12.3055 sinØ = .17238... Ø = 9.9266.. direction angle would be S (45-9.93)° E ...
*September 10, 2014*

**Math Problem (please help)**

rate = 8.12/115.99 = .070006035 but since the $8.12 was most likely rounded off to the nearest cent, I would say it was .07 or 7% so y = .07x so when x = 530.50 y = .07(530.50) = $37.14
*September 10, 2014*

**Math!**

mmmhhh, let's see if 2 hours make sense. to go another 2 hours at 55 mph, would take you another 110 miles, but you already went 275, so you went 110 + 275 or 385 miles. Looks like you stood up your friend. Why not just solve the simple equation given??? 55h + 275 = 440 ...
*September 9, 2014*

**Math**

2[4(9-7)+1]/3 = 2[4(2)+1]/3 = 2[8+1]/3 = 2[9]/3 = 18/3 = 6
*September 9, 2014*

**Math Problem (please help)**

I = kA when A = 4250, then I = 106.25 106.25 = k(4250) k = 106.25/4250 = .025 I = .025A
*September 9, 2014*

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