Monday
March 2, 2015

Posts by Reiny


Total # Posts: 29,207

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

Algebra/Math
f(x) = 3x + b f^-1 (x) = (x - b)/3 (-3, a) lies on both so f(-3) = -9 + b = a f^-1(-3) = (-3-b)/3 = a (-3-b)/3 = -9+b -3-b = -27 + 3b 24 = 4b b = 6 then a = -9+6 = -3 a = -3, b = 6 check my arithmetic
November 6, 2014

Calculus-Newton Method Approximation
1/ 3(x^3) + 1/2(x^2) + 1 = 0 times 6 2x^3 + 3x^2 + 6 = 0 let y = 2x^3 + 3x^2 + 6 dy/dx = 6x^2 + 6x according to Newton's method newx = x - y/y' = x - (2x^3 + 3x^2 + 6 )/(6x^2 + 6x) = (6x^3 + 6x^2 - 2x^3 - 3x^2 - 6)/(6x^2 + 6x) = (4x^3 + 3x^2 - 6)/(6x^2 + 6x) using my ...
November 6, 2014

Math/Algebra
let's find their intersection points 1+x^2+x^3 = 3-x^2+x^3 2x^2 = 2 x^2 = 1 x = ± 1 if x = 1, y =1+2+1 = 3 if x = -1, y = 1 + 1 - 1 = 1 They intersect at (1,3) and (1,1) so what is the difference between their y values ?
November 6, 2014

Algebra
√((x-2)^2 + (y-7)^2 = 13 square both sides and expand x^2 - 4x + 4 + y^2 - 14y + 49 = 169 x^2 - 4x + y^2 - 14y = 116 but x = 10+2y sub that into the first equation (10+2y)^2 - 4(10+2y) + y^2 - 14y = 116 100 + 40y + 4y^2 - 40 -8y + y^2 - 14y = 116 5y^2 + 18y - 56 =0 (y-2...
November 6, 2014

Math
So we are going to need those intercepts, the x - intercepts are easy x = 3 or x = -2 for the y-intercept, let x = 0 y = (-3)^2 (2) = 18 so the points of the triangle are (3,0), (-2,0) and (0,18) so the base of the triangle is 5 and the height is 18 area = (1/2)(base)(height...
November 6, 2014

statistic
a) prob(red) = .546 prob(not red) = .454 prob(exactly 5red) = C(12,5) (.546)^5 (.454)^7 = appr .153 b) prob (green) = .395 prob(not green) = .605 prob(at least 3 green) = prob(3green) + prob(4 green) + ... + prob(12 green) =1 - prob(0 not green) - prob(1 not green) - prob(2 ...
November 6, 2014

math
c is wrong 3^3 = 27 , so 27 is a perfect cube.
November 6, 2014

geometry
what is 8/9 yards ?
November 6, 2014

Math
I suspect you meant: c(t) = 9 - 90 000 (1/ (10 000 + 3t) ) I will also assume that c(t) is in kg/m^3 then 6 = 9 - 90 000 (1/ (10 000 + 3t)) 90000(1/(10000+3t)) = 3 30000 + 9t = 90000 9t = 60000 t = 6666 2/3 minutes ? check my arithmetic
November 6, 2014

Trigonometry
Did you make your sketch? Mine is triangle ABC with angle A = 55° angle C = 22°, and angle B + 103° then it is just a matter of the sine law: AC/sin103 = 300/sin22 I got AC = appr 780 miles
November 6, 2014

geometry
There would be an infinite number of such triangles. What part of the instructions are you having difficulties with ?
November 6, 2014

Maths
make your sketch draw a horizontal line from the top of the shorter pole to the other pole. You now have a right-angled triangle with base 12 m, height 18-13 or 5 m You should recognize the common 5,12, 13 right-angled triangle, if not c^2 = 12^2 + 5^2 = 169 c =√169 = 13
November 5, 2014

Algebra
adults --- x children -- y seniors --- z x+y+z = 895 , #1 14x +11y + 8z = 10514 , #2 translation of: "If the combined number of children and adult tickets exceeded twice the number of senior citizen tickets by 295" ---> x+y > 2z by 295 x+y = 2z + 295 x + y - 2z...
November 5, 2014

Trig
"A playground slide starts 107cm above the ground and is 250cm long" Trusting my English grammar somewhat, you made "slide" the subject of your sentence, and you said it is 250 cm long. Thus 250 is the hypotenuse. tanØ = opposite/adjacent sinØ...
November 5, 2014

Trig
Assuming the slide is a straight line, (most are not) Did you make your sketch? I have the opposite as 107 and the hypotenuse as 250 so sinØ = 107/250 Ø = appr 25°
November 5, 2014

please help, math question
let the width of the matte be x all around so the width of the whole picture = 10+2x and the length is 15+2x area of whole picture = (10+2x)(15+2x) area of picture = 10(15) = 150 area of matte only = (10+2x)(15+2x) - 150 so (10+2x)(15+2x) - 150 = 150 150 + 20x + 30x + 4x^2 - ...
November 5, 2014

Algebra 2
let x be the larger then the smaller is 96-x x - (96-x) = 17 x - 96 + x = 17 2x = 113 x = 56.5 larger is 56.5 , the smaller is 39.5 check: difference = 56.5-39.5 = 17 , yup!!
November 5, 2014

Vertex, Focus, & Directrix of Parabolas
Just did this for Kayla http://www.jiskha.com/display.cgi?id=1415240099
November 5, 2014

Math
x( 1 - 1.02^-11)/.02 = 1700 x( 9.786848.. = 1700 x = $ 173.70
November 5, 2014

Algebra II
writing it in terms of y first of all 48y = x^2 - 12x + 276 or 48y = x^2 -12x + 36 - 36 + 276 48y = (x - 6)^2 + 240 y = (1/48) (x-6)^2 + 5 so the vertex is (6,5) the x of the focus is the same as that for the vertex so x = 6 for y = (1/48)x^2 - (1/4)x + 23/4 the y of the focus...
November 5, 2014

Math HELP!
What did we do to the 7 to make it a 2 ? looks like we subtracted 5 What did we do to the -3 to turn it into a 5 ??? so (x,y) ---> (x-5, ..........) I am sure you can get this
November 5, 2014

math
I did this same problem 2 years ago http://www.jiskha.com/display.cgi?id=1352760453 Looks like this teacher is just recycling the same problems
November 5, 2014

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