Saturday
November 22, 2014

Posts by Reiny


Total # Posts: 27,929

Probability.. HELP!
what is 36x35x34 ? Do you know why ?
November 13, 2014

Math, Please Help!
I will assume we are not distinguishing between small and capital letters. I will do one: TENNESSEE - 9 total, 2 N's , 4 E's, 2 S's total number of ways = 9!/(2!4!2!) = 3780 Can you see what I did ? OHIO ----> 4!/(2!) = 12 try the others.
November 13, 2014

College Algebra
If you mean (-10-6i) /( -9+9i) , then the brackets are essential (-10-6i) /( -9+9i) = (-10-6i) /( -9+9i) * (-9-9i)/(-9-9i) = (90 + 90i + 54i + 36i^2)/(81 -81i^2) = (54 + 144i)/162 = 1/3 + (8/9)i
November 13, 2014

College Algebra
type it this way: (-6 - √10)/(3 + 8√10) I will assume you are rationalizing (-6 - √10)/(3 + 8√10) = (-6 - √10)/(3 + 8√10) * (3 - 8√10)/(3 - 8√10) = (-18 + 48√10 - 3√10 + 80)/(9 - 640) = ( 62 + 45√10)/-631 = (-62...
November 13, 2014

Calculus
are you using the usual notation so that a(t) is acceleration, v(t) is velocity and s(t) is distance ?? I will assume you are a(t) = t^2 - 8t + 5 v(t) = (1/3)t^3 - 4t^2 + 5t + c s(t) = (1/12)t^4 - (4/3)t^3 + (5/2)t^2 + ct + k s(0) = 0 0-0+0+0+k=0 k=0 s(1) = 20 1/12 - 4/3 + 5/2...
November 13, 2014

algebra
looks like we are dividing by -2 each time, so ....
November 13, 2014

algebra
So a is always positive and b is always negative. What is a positive divided by a negative ?
November 13, 2014

Algebra
if f(x) = 4x^7+x^5+3x^2-2x+c f(-1) = -4 -1 + 3 +2 +c = 0 c = 0
November 13, 2014

math
Since the area of each time is 16 in^2, each side of the tile must be 4 inches the table is 6 ft by 6ft or 72 inches by 72 inches so we need 72/4 or 18 tiles along a side. since the table is square, the number of tiles needed = 18(18) 324 tiles
November 13, 2014

Math
I usually get rid of nasty decimals ... .1g+3.75m=7.36 --> 10g + 375m = 736 --> g = (736-375m)/10 8.2g+21m=73 ----> 82g + 210m = 730 10g +375m = 736 -times 410 --> 4100g + 153750m = 301760 82g + 210m = 730 -times 50 --> 4100g + 10500m = 36500 subtract them: ...
November 13, 2014

math
I think Bob has a typo in dividing x+y+z by 2 instead of 3 x+y+z+ (x+y+z)/3=360 3x+3y+3z + x+y+z = 1080 4x+4y+4z = 1080 x+y+z = 270
November 13, 2014

Algebra 2
3x^2 - 24x + 45 = 0 remember Steve told you about all that "zero stuff" ? divide each term by 3 x^2 - 8x + 15 = 0 can you think of 2 numbers that add up to -8 and multiply to get 15 ? I am thinking -3 and -5 so (x-3)(x-5) = 0 x-3=0 ----> x = 3 or x-5 = 0 ----> ...
November 13, 2014

math
Proof for all values: let a+b+c+d+e = S let M be the average M = S/5 5M = S then S/M = 5/1 or S : M = 5 : 1
November 13, 2014

Math
correct
November 13, 2014

algebra. help!
first one: y = 2^x why did you possible pick c) not a single one of the pairs given satisfies that equation. It is clearly y = (x+3)^2 , that is, d)
November 13, 2014

Algebra
number of $1 --- n number of $2 --- n+11 number of $3 --- n-18 now for the "value" : 1n + 2(n+11) + 3(n-18) = 100 n+2n+22 + 3n-54 = 100 6n = 132 n = 22 then n+11 = 33 n-18 = 4 so 22 $1 bills , 33 $2 bills and 4 $3 bills check: 22 + 66 + 12 = 100 Yeahh
November 13, 2014

Algebra
surely you can replace x with 2 and add 2+6
November 13, 2014

Algebra
in h(x) = −9x^3+3x^2−2x+2 they are in order of decreasing degree
November 13, 2014

Algebra
h(x) = −9x^3+3x^2−2x+2 why did you put commas between terms in your answer ?
November 13, 2014

math
cost = 16m + 1895 , where m is the number of miles and cost is in cents 16m + 1895 = 5000 16m = 3105 m = appr 194 miles check: 194(.16) + 18.95 = 49.99
November 13, 2014

Algebra 2
As Morgan pointed out, your left side is a perfect square (x+4)^2 = 16/9 x+4 = ± 4/3 x = 4/3 - 4 = -8/3 or x = -4/3 - 4 = -16/3 your signs were wrong
November 13, 2014

algebra
tom has x stickers Matt has 6x stickers there must have been a total of 140 stickers x + 6x = 140 7x = 140 x = 20 Tom has 20 and Matt has 120 So Matt has to give 50 of them to Tom check: Tom: 20+50 = 70 Matt: 120-50 = 70 Yeahhh
November 13, 2014

Trig/Pre-Calc
try x = ±1 , ±2, ±4, ±8 I got x = 8 to work for me so after a sythetic division, I got (x-8)(15x^2 + x - 2) = 0 (x-8)(3x-1)(5x + 2) = 0 x = 8 , 1/3 , -2/5
November 13, 2014

math
same type of problem as your previous one
November 13, 2014

math
What is 9 ÷ (3/8) ?
November 13, 2014

chin
That is a "serious" problem I will use A for ace F for facecard and L for non-ace, non-face (L for loser) I will also assume that none of the 4 cards drawn in a game are returned to the deck, but they would be returned after a game is played. so the possible ...
November 13, 2014

maths algebra
I think you are referring to this earlier post by you http://www.jiskha.com/display.cgi?id=1415787409 I agree with Steve's answer, I subbed his answer back in the original equation, and it worked. Steve's solution was correct, perhaps you typed it incorrectly. As to ...
November 13, 2014

math
Just translate the English into Math "Half the total number of balls are pink. " ----> p = (1/2)(r+b+g+p) 2p = r+b+g+p p = r+b+g , #1 "One-fourth of the number of green balls equals one-third of the numher of blue balls. " ----> (1/4)g = (1/3)b 3g = ...
November 13, 2014

Algebra
amount = 19 (1/2)^(150/97) = appr 6.5 g
November 13, 2014

math
look at Steve's solution here http://www.jiskha.com/display.cgi?id=1382123644 then change the numbers to fit your problem
November 12, 2014

math
at a time of t minutes, let the radius of the water level be r cm let the height of the water level be h cm by ratios: r/h = 1.75/6 1.75h = 6r r = 1.75h/6 = 7h/24 V = (1/3)π r^2 h = (1/3)π(49h^2/576)h = (49π/1728) h^3 dV/dt = (49π/576) h^2 dh/dt without ...
November 12, 2014

calculus
total distance = 24 + 24(.95) + 24(.95)^2 + .... an infinite GS, where a = 24 and r = .95 sum(all terms) = a/(1-r) = 24/(1-.95) = 24/.05 = 480 metres
November 12, 2014

Calculus
nope, I have no idea how you got that. use the product rule, y = x secx y' = x(secx)(tanx) + secx or = x(1/cosx)(sinx/cosx) + 1/cosx = xsinx/cos^2 x) + 1/cosx or = (xsinx + cosx)/cos^2 x so slope = (π/4)(√2/2) + √2/2)/(1/2) = .....
November 12, 2014

finance math
Assumption: the rate stays at 7% throughout her 31 years of deposits and the 15 years of withdrawals. (What happens after the 15 years of retirement and her money is used up ? ) let her payment + employers share be $x per year x( 1.07^31 - 1)/.07 = 30000(1 - 1.07^-15)/.07 you ...
November 12, 2014

Math
so in your equation, y is the number of words and x is the number of minutes so set y = 2500 50x - 25 = 2500 50x = 2525 x = 50.5 so it will take 50.5 minutes or 50 minutes and 30 seconds.
November 12, 2014

Algebra
Trish, since subtraction only involves "like" terms, and g(x) does not contain any x^4 term, nothing can happen to the x^4 term of f(x) so your result still contains the x^4 term , and thus is a polynomial of degree 4
November 12, 2014

Math
Well, I would suggest you do each division and see.
November 12, 2014

Math
Your question asked for the slope, you gave the equation as an answer. I can tell that you found the slope to be 35, which is correct. Also the equation is correct
November 12, 2014

Algebra 2
Neither equation you state is a quadratic equation for the first, we could attempt to write it as 0x^2 + 5x - 6 = 0 , but when we attempt to use the formula x = (-b ± √(b^2 - 4ac) )/2a we get x = (-5 ± √(25 - 0)/0 = 0/0 , which of course causes all ...
November 12, 2014

Math
good job !
November 12, 2014

Math
yes, I would get y - 100 = (100/3)(x - 3) times 3 3y - 300 = 100x - 300 100x - 3y = 0 or y = (100/3)x
November 12, 2014

Math
I would simplify that ... 50/1.5 = 100/3 Normally we don't mix decimals with fractions, use either one or the other. your answer technically is correct
November 12, 2014

Algebra
If you were to fully expand this, your unsimplified line would consist of 27 terms - that is, any combination of terms in the first bracket times any term in the second bracket times any term in the third bracket the only way to get x^3 is to have -3 from the first times -3x ...
November 12, 2014

Algebra
so ( p(x) )^3 = (x^4-3x+2)(x^4-3x+2)(x^4-3x+2) now consider which combination can produce a term ending in x^3 ??
November 12, 2014

Algebra
so f(x) has to contain an x^4 term and g(x) does NOT contain an x^4 term so what happens to that x^4 term in f(x) when g(x) is subtracted from it ???
November 12, 2014

math
let the base be x by y m V = (x)(y)(1) = xy xy = 9 y = 9/x cost = 50xy + 60xy + 2(40x) + 2(40y) = 110xy + 80x + 80y = 110x(9/x) + 80x + 720/x = 110 + 80x + 720/x d(cost)/dx = 80 - 720/x^2 = 0 for a min of cost 80x^2 = 720 x^2 = 9 x = 3 then y = 9/3 = 3 the box should be 3 by 3...
November 12, 2014

Math Help!!!
1. 1/2 is rational, thus real (any rational is automatically real) -1.016879413894 --- can't tell from the way it was typed. No repetition is apparent, but no indication is given that it continuous. If it terminates the way it was typed, then it is rational the last two ...
November 12, 2014

Algebra
amount = 4500(1 + .045/365)^3650 = 7057.21 or $ 7057 to the nearest dollar
November 12, 2014

Math
Each of the sides must be 10 m The longer diagonal creates an isosceles triangle with angles 30,30 and 120° Several ways to do this 1. Construct a perpendicular which will bisect the diagonal. Let the diagonal be 2x then x/10 = cos30° x = 10cos30 = 8.66.. 2x = 17.32 m ...
November 12, 2014

ap calc
so far ok -3sin(x)-2cos(x)=0 3sinx = -2cosx sinx/cosx = -2/3 tanx = -2/3 construct your triangles in quad II and IV for both the hypotenuse is √13 in quad II y = 3(-3/√13) - 2(2/√13) = -13/√13 in quad IV y = 3(3/√13) -2(-2/√13) = 13/√...
November 9, 2014

ap calc
First of all, since (1,4) is on the curve, 4 = a + b dy/dx = a - b/x^2 = 0 for a max or min but we are told that this is true when x = 1 so a - b/1 = 0 a - b = 1 add them, 2a = 5 a = 5/2 sub back into the first equation, a+b=4 5/2 + b = 4 b = 3/2 a = 5/2 , b = 3/2
November 9, 2014

Math
by Pythagoras, you can find MW = 12 then cosW = 12/13
November 9, 2014

college algebra
same post
November 9, 2014

college algebra
x^4 +12x^3 +10x^2-9x+9x+22=0 I suspect a typo, why would you have two x terms without combining them?
November 9, 2014

calculus
y' = (4x+3)^5 (-4)(5x+2)^-5 (5) + (5x+2)^-4 (5)(4x+3)^4 (5) = -20(4x+3)^5 (5x+2)^-5 + 20(4x+3)^4 (5x+2)^-4 take it further if there is need by taking out a common factor of 20(4x+3)^4 (5x+2)^-5
November 9, 2014

Math - Word problem
Mary, your problem is a variation of the famous "spider and fly" problem. Here is a webpage that has the same concept, you have an electrical outlet and box instead of spider and fly. http://mathworld.wolfram.com/SpiderandFlyProblem.html Use Steve's instructions ...
November 9, 2014

Algebra 2
you just proved my point, you forgot to switch back to one of your other names
November 9, 2014

Algebra 2
Don't change names, stick to one name follow the same steps I showed you yesterday for the same type of problem http://www.jiskha.com/display.cgi?id=1415491412 expand first, then bring everybody to the left and factor. Remember the right side has to be zero.
November 9, 2014

Algebra 2
follow the same steps I showed you yesterday for the same type of problem http://www.jiskha.com/display.cgi?id=1415491412 expand first, then bring everybody to the left and factor. Remember the right side has to be zero.
November 9, 2014

calculus
follow the steps I just showed you for your previous problem (same thing)
November 9, 2014

calculus
f(f(x)) = f(4x^2 - 1) = 4(x^2 - 1)^2 - 1 don't know if you have to expand that, leave that up to you g(f(x)) = g(4x^2 - 1) = 4/(4x^2 - 1)
November 9, 2014

average
Reverse your thinking. How do you think they found the average of those 4 numbers to be 36 ?
November 9, 2014

Calc
notice the point (4,0) does not lie ON the curve. So your sketch should show that. let that point be (a,b) so we know b = √a or a = b^2 dy/dx = (1/2)x^(-1/2) or 1/(2√x) so at the point (a,b) the slope of the tangent is 1/(2√a) I will use the property that at ...
November 9, 2014

math
number of men --- m number of women --- w number of children --- c m+w+c = 180 , #1 m = 2w , #2 w = 3c , #3 from #2 , w = m/2 then in #3, 3c = w c = (1/3)w = (1/3)(m/2) = m/6 back in #1 m+w+c = 180 m + m/2 + m/6 = 180 times 6 6m + 3m + m = 1080 10m= 1080 m = 108 then w = m/2...
November 9, 2014

Calc
why not just state the equation of the parabola, then we can do the question
November 9, 2014

Algebra
you want g(x) = g(x) , so x^3 + x^2 + x - 1 = x^3 - x^2 + x + 1 2x^2 = 2 x^2 = 1 x = ± 1 if x = 1 , g(1) = 1 - 1 + 1 + 1 = 2 if x = -1 , g(-1) = -1 - 1 - 1 + 1 = -2 so they intersect at (1,2) and (-1,-2)
November 9, 2014

Algebra
Are we to assume that your line AB is a straight line? If so, we can find the slope of AB slope AB = (b^2 -a^2)/(b-a) = (b-a)(b+a)/(b-a) = b+a we can write the equation as y - a^2 = (b+a)(x-a) also (3/2,0) lies on it, so 0-a^2 = (b+a)(-3/2 - a) -a^2 = -3b/2 -ab - 3a/2 - a^2 3b...
November 9, 2014

maths
I made a sketch and it looks like a simple cosine law problem d^2 = 10^2 + 3^2 - 2(10)(3)cos135 = 151.426... d = 12.3 km/hr then to find the small acute angle Ø sinØ/3 = sin 135°/12.3.. sinØ = .1723.. Ø = 9.927° direction is S (45-9.927..)&...
November 9, 2014

Trigonometry
if you want the direct line distance (along the hypotenuse) sin 19.5 = 939/d d = 939/sin19.5 = 2813 m If you want the horizontal displacement tan 19.5 = 939/x x = 939/tan19.5 = 2652 m to the nearest metre
November 8, 2014

Algebra 2
x^2 - 13x +40 = x x^2 - 14x + 40 = 0 (x-10)(x-4) = 0 x = 10 or x = 4
November 8, 2014

Algebra 2
expand it first 4x^2 - 24x - x^2 + 2x + 24 = 0 3x^2 - 22x + 24 = 0 (x-6)(3x - 4) = 0 x = 6 or x = 4/3
November 8, 2014

Algebra 2
probably the most method used for 3by3 equations is called elimination The object is to eliminate one or more variables from pairs of equations. Usually we look at the coefficents of each variable and choose the one with the smallest or simplest numbers. In this case it doesn...
November 8, 2014

Trigonometry
No idea where A , B , or C are
November 8, 2014

arithmetic
First of all, you are using the formula for a geometric, yours is an arithmetic Secondly, the sentence "the 20th sum of an arithmetic progression is -7 and the sum of the first 20 terms is 620" makes no sense to me what does "the 20th sum" mean ?
November 8, 2014

Trigonometry
diagrams don't show up in this format You will have to give a good description
November 8, 2014

math
yes, that is one of the rules of powers e.g (2x3)^4 = (2^4)(3^4) =(16)(81) =1296 or (2x3)^4 = 6^4 = 1296
November 8, 2014

math
a) two cases: bw or wb case 1: first ball is b, prob(b) = 7/12 so 3 black balls are added, now we have 5 w, 10 b prob(w) = 5/15 = 1/3 prob(case1) = (7/12)(1/3) = 7/36 case 2: first ball is w, prob(w) = 5/12 so 3 white balls are added, now we have 8w, 7b prob(b) = 7/15 prob(...
November 8, 2014

math
How can you get a sum of 10 on 2 dice ? only ways: 4,6 6,4 5,5 and there are 36 ways for the 2 dice to fall, so prob(sum of 10) = 3/36 = 1/12 btw "throne" ---> thrown
November 8, 2014

Intermediate Algebra
amount at 6% === x amount at 14% ---- 17000-x solve for x .06x + .14(17000-x) = 1500 I would multiply each of the 3 terms by 100 to get rid of the decimals 6x + 14(17000-x) = 150000 etc
November 8, 2014

equation
a is 30% of b --- > a = 3/10b 3b = 10a b = 10a/3 = (10/3)a = 3.3333..a = 333 1/3 % a
November 7, 2014

AP CALC. AB
a) let the height of the sand in the box be h inches V= (40)(20)(h) = 800h dV/dt = 800 dh/dt -300 = 800dh/dt dh/dt = -300/800 = -3/8 inches per minute b) part 2 V = (1/3)π r^2 h dV/dt = (13)π r^2 dh/dt + (2/3)π r h dr/dt plugging in our information ... 300 = (1/...
November 7, 2014

math again (last question help!!!)
first one --x 2nd one -- y 3rd one -- 35-x-y x+y = 20 y + (35-x-y) = 28 --- > x = 7 (then 7+y =20 ---> y = 13 35-x-y = 35-7-13 = 15 first shelf has 7 2nd shelf has 13 third has 15 check: 1st plus 2nd = 7+13 = 20 , check! 2nd plus 3rd = 13+15 = 28, check! all is good
November 7, 2014

Math
x(1.0225)^30 = 50000 solve for x to get x = 25649.00
November 7, 2014

Math Trig Please Help!!!
Make a real effort to memorize the trig ratios for these basic right-angled triangles 45-45-90 degree triangle ---> 1 -- 1 -- √2 30-60-90 degree triangle ---> 1 -- √3 -- 2 make a quick sketch of these triangles, It is easy to see where the values go. Remember...
November 7, 2014

Math
sin^-1 .5 = .5236 radians sin(.5^-1) = sin(2) = .909297 (sin .5)^-1 = .47942..^-1 = 2.08583
November 7, 2014

Math Help!
treat (2Ø+8) as you angle then, do tan^-1 (.489) = x x = .45481 radians but the tangent was negative so 2Ø+8 = π-.45481 2Ø = -5.313216.. Ø = -2.65661 or 2Ø+8 = 2π-.45481 Ø =-1.0858.. as you can see those two answers are ...
November 7, 2014

Math Trig Help
recall that sinØ = opposite/hypotenuse = x/3 so you have a right angled triangle with opposite = x and hypotenuse = 3 let the adjacent be a a^2 + x^2 = 3^2 a^2 = 9 - x^2 a = ± √(x^2 - 9) , but Ø is in I, so a = √(x^2 - 9) cosØ = √(...
November 7, 2014

Math
sinØ = 1/4, so opposite = 1, hypotenuse = 4 by Pythagoras, adjacent = √15 secØ = 1/cosØ = 1/(√15/4) = 4/√15 tan Ø = 1/√15
November 7, 2014

Math
sec 7pi/4 = 1/cos(7π/4) 7π/4 is in quad IV, where the cosine is positive 7π/4 is π/4 away from the x-axis so cos7π/4) = 1/√2 so sec 7π/4 = √2
November 7, 2014

Math
here is my answer from 2 years ago http://www.jiskha.com/display.cgi?id=1351706906 there are other answers in the "Related Questions" below
November 7, 2014

Math
use the same webpage I just gave you for c) , enter y = x^3
November 7, 2014

Math
play with with by editing the equation in the subject box http://www.wolframalpha.com/input/?i=y+%3D+%7Cx-2%7C
November 7, 2014

Math Question
slope = (4-(-2))/(-2-3) = -6/5 y+2 = (-6/5)(x-3) 5y+10 = -6x + 18 6x + 5y - 8 = 0 or 6x + 5y = 8 or y = (-6/5)x + 8/5
November 7, 2014

algebra and geometry
if 1 inch ---> 4 ft then 2 inches by 5 inches ---> 8 ft by 20 ft
November 7, 2014

math
Looks like a simple case of Pythagoras d^2 = 15^2 + 8^2 = 289 d = √289 = 17 m
November 7, 2014

math
You will have to know to how many decimal places you want to round. best shown with an example 12.3567 suppose you are asked to round to 3 decimal places. Look at the 4th decimal place. If that is from 0 to 4, the digit in the 3rd decimal stays the same. If the 4th decimal is ...
November 7, 2014

mathematics
volume of cylinder is area of base x height since you are given both of these, just sub in and do the arithmetic.
November 7, 2014

math
present: Mario's age --- x Bert's age ----- 2x+5 Nine years ago: Mario --- x-9 Bert ---- (2x+5) - 9 = 2x -4 "Nine years ago, the sum of their ages is 50. " ----> x-9 + 2x-4 = 50 3x = 63 x = 21 Mario is now 21 and Bert is now 47 check: 9 yrs ago Mario was ...
November 7, 2014

Calculus
from xy^2 = 16 y^2 = 16/x now sub that into F = x^2 + y^2 = x^2 + 16/x dF/dx = 2x - 16/x^2 = 0 for max/min 2x - 16/x^2 = 0 2x = 16/x^2 2x^3 = 16 x^3 = 8 x = cuberoot(8) = 2 if x = 2 , y^2 = 16/2 = 8 ---> y = ±√8 or ±2√2 then F = x^2 + y^2 = 4 + 8...
November 6, 2014

Intermediate Algebra
why did you switch signs ??? x3 – 380x2 + 2x – 760 = 0 x^2(x - 380) + 2(x - 380) = 0 (x - 380)(x^2 + 2) = 0 x = 380 or x^2 = -2 , the latter has x not a real number so x = + 380
November 6, 2014

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