Saturday

November 22, 2014

November 22, 2014

Total # Posts: 27,927

**Algebra**

since each bracket has a +1 understood in front of it, you can just drop the brackets. Collect all like terms and you are done
*October 2, 2014*

**Math 3 quick questions**

For the first two, do you notice that the binomial appears both as a square and as a first degree expression? When you first learn to do these types, it might be a good idea to replace the binomial with a single variable. e.g. in the first: let 3x+1 = a , then your equation ...
*October 2, 2014*

**algrebra**

number of dimes --- x number of quarters --- x+17 value of money: 10x + 25(x+17) = 600 , all in cents 10x + 25x + 425 = 600 35x = 175 x = 5 so 5 dimes and 22 quarters. check by finding the value of 5 dimes and 22 quarters.
*October 2, 2014*

**Math**

14 g = 53 L 1 g = (53/14) L then 25 g = (53/14)(25) L = appr 94.6 L
*October 2, 2014*

**Math**

what happens when you multiply something by 10? what happens when you multiply something by 100? by 1000? etc so look at 60x50 as 6x10 x 5x10 = 6x5x10x10 = 30x100 = 3000
*October 2, 2014*

**geometry**

You are obviously looking at some diagram, which we can't see.
*October 2, 2014*

**math**

It is unfortunate that measurement of angles, and time, has escaped the metric system. Things would be so much easier. K = 90° - 48° 26' 8" = 89° 59' 60" - 48°26'8" = 41° 33' 52" Hint: If you have a good scientific ...
*October 2, 2014*

**HELP! Algebra. DONT UNDERSTAND**

Niezel is correct from a - e explanation of e) (a+b)(c+1)-(a+b) = ac+bc = c(a+b) by common factor of (a_+b) = (a+b)(c+1 - 1) = c(a+b) f) x^2 - 9y^2 ----- standard difference of squares = (x+3y)(x-3y) g) (x^2 - y^2) + x + y = (x-y)(x+y) + (x+y) , difference of squares at the ...
*October 2, 2014*

**Financial Mathematics**

i = .07/12 = .0058333... (I stored that in memory on my calculator for good accuracy) 2000(( 1.0058333..^20 - 1)/.0058333)(1.0058333..)^40 + 2500( (1.00583333..^20 - 1)/.0058333..)(1.0058333..)^20 + X(1.005833..^20 - 1)/.0058333.. = 180000 , X = 2000+R 53375.555 + 59392.5459...
*October 2, 2014*

**Probability**

a) prob(red) = 5/10 = 1/2 b) prob(red or white) = 7/10 c) prob( as stated) = 5/10 or 1/2 , there are still 10 balls, since you replaced it whatever happened in first draw has no effect on the second draw d) prob( as stated) = 5/9 , now it matters, there are only 9 balls left e...
*October 2, 2014*

**math**

First of all the area of a circle is π r^2 , not (πr)^2 so πr2= 658 r^2 = 658/π r = √(658/π) = appr 14.47
*October 1, 2014*

**Math**

prob(fail) = 6/100 = 3/50 prob(not fail) = 47/50 prob(2 of 6 will fail) = C(6,2) (3/50)^2 (47/50)^4 = appr .042 Since the prob (anything) must be a number from 0 to 1, your answer makes absolutely no sense at all. I don't even understand your notation.
*October 1, 2014*

**Math**

y - y1 = mx - mx1 mx1 = mx - y + y1 x1 = (m - y + y1)/m
*October 1, 2014*

**Trigonometry**

safe ramp: tanØ = 1/12 Ø = 4.76° Since your angle is greater than that, it is not safe
*October 1, 2014*

**Math**

4√(1280r^4t^12) = 4√1280 √r^4 √t^12 = 4(16√5)r^2 t^6 = 64√5 r^2 t^6
*October 1, 2014*

**Math Definition Help**

Definitions are easy to check Let Google or your texbook be you friend.
*October 1, 2014*

**Math Help**

I will assume you meant f(x) = (3x+4)/5 or y = (3x+4)/5 step1: interchange the x and y variables x = (3y+4)/5 step2: solve this inverse equation for y 5x = 3y + 4 3y = 5x - 4 y = (5x-4)/3 f^-1 (x) = (5x-4)/3
*October 1, 2014*

**Pre-Calc**

A and B are inverses. (you can check by picking any number, subbing that into the original function. Take that answer and sub it into the "inverse" function. If you don't get back the original number it is not a true inverse. e.g. for D let x = 3 f(3) = 7 f(7) = ...
*October 1, 2014*

**MATH**

I will assume you meant: ln ( (3x-2)/(x-1) ) < 0 I would establish the boundary by letting ln ( (3x-2)/(x-1) ) = 0 then (3x-2)/(x-1) = e^0 , yes e^0 = 1 (3x-2)/(x-1) = 1 3x-2 = x-1 2x = 1 x = 1/2 So we need either x < 1/2 or x > 1/2 But remember x = 1 is not allowed ...
*October 1, 2014*

**Math**

1. Use the sum of n terms of an arithmetic sequence sum = (n/2)(first + last) (16/2)(first + 12500) = 800000 divide by 8 first + 12500 = 80000 first = 80000-12500 = 67500 2. museum A: a = 50,000 , d = 2500 museum B: a = 45,000 , d = 2750 find term(12) or a+11d for each one ...
*October 1, 2014*

**Maths**

Your formula makes no sense, because I could just cancel the d's and get l = k check your typing. Is there a square root somewhere I suspect something like: " intensity is proportional to the square of the distance"
*October 1, 2014*

**Pre Calculus**

I did the same question on Monday http://www.jiskha.com/display.cgi?id=1412031500
*October 1, 2014*

**MATH**

Lena,did you not check your answer? It does not work, mine does. Always check your results by testing them for the original conditions 14(.25) + 22(.50) ≠ $15.00
*September 30, 2014*

**MATH**

You should check your "caps lock" key, it appears to be stuck. number of 1/2 cups ---- x number of whole cups --- 37-x 25x + 50(37-x) = 1500 25x + 1850 - 50x = 1500 -25x = -350 x = 14 etc
*September 30, 2014*

**7th grade math**

Correct, there are 10 of them and you found them all
*September 30, 2014*

**Math**

Here is how I would do this in a formal way: Would like to have a zero on the right side, so ((3x-2)/(x-1))<1 ((3x-2)/(x-1))-1 < 0 (3x-2 - (x-1))/(x-1) < 0 (2x - 1)/(x-1) < 0 "critical values" are x = 1/2 and x = 1 This splits a number line into 3 parts, ...
*September 30, 2014*

**math**

helicopters --- H airplanes ----- 4H H+4H = 35 5H = 35 H = 7 so .....
*September 30, 2014*

**Math .**

#1 yes #2: a+5 = (1/5)(5a+25) a+5 = a+5 ----> 5=5 , statement is true infinite number of solutions #3 3(4x - 3) - 7x = 5x - 9 12x-9-7x=5x-9 5x-9 = 5x-9 true, so infinite number of solutions #4 yes
*September 30, 2014*

**Calculus**

the original fractions had 7 and 5 in the denominator which is the same as (1/7) times .... e.g 9/4 = (1/4)(9)
*September 30, 2014*

**Calculus**

recall that if y = secx dy/dx = secx tanx y= [(sec^7 x)/7] - [(sec^5 x)/5] dy/dx = (1/7)(7)(sec^6 x)(secx)tanx - (1/5)(5)(sec^4 x)secx tanx = sec^7 x tanx - sec^5 x tanx = sec^5 x tanx(sec^2 x - 1) but sec^2 x - 1 = tan^2x = (sec^5 x)(tan^3 x) nice question
*September 30, 2014*

**Pre-caluclus**

so ln(x-2e)+ln(x-3e)=2 ln ( (x-2e)(x-3e) ) = 2 by definition (x-2e)(x-3e) = e^2 x^2 - 5ex + 6e^2 - e^2 = 0 x^2 - 5ex + 5e^2 = 0 x = (5e ± √(25e^2 - 4(1)(5e^2))/2 = (5e ± √5e^2)/2 = (5e ± e√5)/2 = ( (5±√5)/2 )e
*September 30, 2014*

**analytic geometry**

horizontal distance --- x I see it as: tan 3.5° = 120/x x = 120/tan3.5 = appr 1962 ft
*September 30, 2014*

**Math**

only one possibility of rolling a number less than 2, namely the number 1 prob(one) = 1/6 number of times this happens rolling 720 times = (1/6)(720) = 120
*September 30, 2014*

**Algebra**

|x+2| < 5 x+2 < 5 AND -x-2 < 5 x < 3 AND x > -7 I always taught this notation: -7 < x < 3 I will let you convert to your notation
*September 30, 2014*

**math**

let's change the room dimensions to inches 14 ft by 20 ft = 168 in by 240 in We can fit 21 tiles along the 168 inches side We can fit 30 tiles along the 240 inches side number of tiles = 21 x 30 or 630 tiles. The solution by Brilliant was not so brilliant, it is wrong ...
*September 30, 2014*

**THEORY OF INTEREST**

let the equivalent nominal rate compounded quarterly be j Consider one year. (1+.087/12)^12 = (1 + j/4)^4 1.00725^3 = 1+j/4 .051908068 = j/4 j = .087632274 or 8.763 %
*September 30, 2014*

**Algebra 2 Answer Check**

nope,, Damon showed you that the slope of your given line is -5/2 Trust him !
*September 30, 2014*

**Math**

1. the inverse of your given relation is (-1,3) , (5,2) , (-4,-4) 2. can you see what I did? I suggest you plot the original points and join them with a line, then plot the new points and join them with a line. Can you see what happened ?
*September 30, 2014*

**Pre-Calculus/Trigonometry**

how about we let f(x) = x^2 g(x) = x/(x+4) then g(f(x)) g(x^2) = x^2/(x^2 + 4)
*September 30, 2014*

**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*

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