Tuesday
September 27, 2016

Posts by Reiny

Total # Posts: 36,030

MAth
24m^9 - 27m^7 - 24m^5 = 3m^5(8m^4 - 9m^2 - 8) so the GCF is 3m^5
July 12, 2016

Maths
your equations are jumbled and garbled did you mean: -7x + 7y = -21 and -9x + 9y = -27 ?? dividing the first one by -7 and the second by -9 produces the same equation, x - y = 3 So they are both one and the same equation. Look up how each of your classifications is defined in ...
July 12, 2016

pre algebra
prob(red) = 1/3 prob(not red) = 2/3 odds in favour of red = (1/3) : (2/3) = 1 : 2
July 12, 2016

math
Assuming a total loss, what is 80% of 288,000
July 12, 2016

Math
There are 69 shells, you said so.
July 12, 2016

Algebra
I agree with PsyDAG Your question makes about as much sense as this one: Sara can drive to Chicago in 5 hours, Jasmin can do the same trip in 7 hours. How long will it take the two of them driving together?
July 12, 2016

pre cal
x^4>4x^2 x^4 - 4x^2 > 0 x^2(x^2 - 4) > 0 x^2(x+2)(x-2) > 0 critical values are -2, 0, +2 for x < -2 , --->(+)(-)(-) >0 , so true for x = 0 , no good for -2 < x <0 , say x = -1 ---> (+)(+)(-) < 0 , false for 0 < x < 2 , ---> (+)(+)(-) &...
July 12, 2016

Calculate y' and y'' at the point (1,1)
Gee, you posted this same question only 3 minutes ago. I know we are fast but .... btw, it has been answered.
July 12, 2016

Math
first derivative: 5x y^2 + 9y - 14 = 0 5x(2y)dy/dx + 5y^2 + 9dy/dx = 0 dy/dx(10xy + 9) = -5y^2 dy/dx = -5y^2/(10xy+9) at (1,1) dy/dx = y' = -5/19 , you had that from 5x(2y)dy/dx + 5y^2 + 9dy/dx = 0 10xy y' + 5y^2 + 9 y' = 0 recall the rule for derivatives of triple...
July 12, 2016

pre cal
Just noticed that Steve answered your question yesterday. http://www.jiskha.com/display.cgi?id=1468295145 Why are you repeating it? (this time with a typo)
July 12, 2016

pre cal
First of all, your equation contains a typo, it should say: h(t)= (−g/2) t^2+v0t+h0 secondly, what units are you using? thirdly, did you drop the rock or did you give it a downwards velocity? let me know before I can answer your question.
July 12, 2016

Math - Studying for Pre Calc exam!
6 sin 2x − 8 cos x + 9 sin x = 6 12sinxcosx - 8cosx + 9sinx - 6 = 0 4cosx(3sinx - 2) + 3(3sinx - 2) = 0 (3sinx - 2)(4cosx + 3) = 0 sinx = 2/3 OR cosx = -3/4, the last one is not possible sinx = 2/3 x = .7297.. which matches b) Make sure your calculator is set to radians ...
July 12, 2016

math
Haven't done this kind of question in over 55 years, had to look it up try this: http://math.stackexchange.com/questions/315317/orthogonal-trajectories-for-a-given-family-of-curves
July 12, 2016

Math
don't like fractions, so how about Ø = x/2 or x = 2Ø then your equation becomes cosØ - sin 2Ø = 0 cosØ - 2sinØcosØ = 0 cosØ(1 - 2sinØ) = 0 cosØ = 0 or sinØ = 1/2 Ø = π/2, 3π/2...
July 12, 2016

Pre-Cal
tan^(2)xsecx+secx = secx( tan^2 x + 1) , common factor = secx(sec^2 x), by identity = sec^3 x (csct-sint)/(csct) = (1/sint - sint)/(1/sint) multiply top and bottom by sint = (1 - sin^2 t)/1 = cos^2 t
July 11, 2016

Pre-Cal:(Cont.)
2 cos 2θ − 1 = 0 cos 2Ø = 1/2 I know cos π/3 = 1/2 , and the cosine is positive in I and IV so 2Ø = π/3 , in I OR 2Ø = 2π - π/3 = 5π/3 , in IV Ø = π/6 or Ø = 5π/6 (Ø = 30° or Ø...
July 11, 2016

Math
I am sure you meant: f(x) = (ax + b)/(cx + d) "the horizontal asymptote is y=2" ----> ax/(cx) = 2 , as x ---> infinity a/c = 2 a = 2c so we have f(x) = (2cx + b)/(cx + d) "the vertical asymptote is x =5" ---> (x-5) <---> cx + d c = 1, d = -5 ...
July 11, 2016

Even or Odd Funciton
let's take your answer a bit further ... 1/((-x)^3-5(-x)) = 1/( -(x)^3 + 5x) = -1/(x^3 - 5x) = - f(x) so the function is odd by definition: odd ---> f(-x) = -f(x) even ---> f(-x) = f(x)
July 11, 2016

calculus
You are correct!
July 11, 2016

calculus
I assume you used: tan(A - B) = (tanA - tanB)/( 1 + tanAtanB) then (tan17pi/12 - tan pi/4) / (1+tan 17pi/12 tan pi/4) = tan(17π/12 - π/4) = tan( 7π/6) or tan 210° ---> quad III = 1/√3
July 11, 2016

math
I am sure you meant: (tan 7x − tan x)/( 1 + tan 7x tan x) compare to : tan(A-B) = (tanA - tanB)/(1 + tanAtanB)
July 11, 2016

math
you should recognize this as the use of cos(A+B) cos 60° cos 65° − sin 60° sin 65° = cos(60°+65°) = cos 125°
July 11, 2016

calculus
poor choices for answers, they should have rationalized the answer. That's where my hint about a calculator comes in. Both our answers were (1/4)(√2 - √6) if you work that out on your calculator you get appr -.2588 working out c) you get appr -.2588 so c) is ...
July 11, 2016

calculus
correct Why not just check your result with a calculator?
July 11, 2016

calculus
60.1 − 43.9 cos πt/ 6 ≥ 77 − 43.9 cos πt/ 6 ≥ 16.9 cos πt/6 ≤ - .38496... consider cos πt/6 = - .38496... I know cos 1.1756.. = +.38496 so πt/6 = π - 1.1756 = appr 1.966 t = 3.755 or πt/6 = π + 1.1756.. = 4....
July 11, 2016

amth
I know cos 30° or cos π/6 = +√3/2 so x/2 = 180-30 or x/2 = 180+30 x = 300° or x = 420° or x = 5π/3 or 7π/3 To do these type of questions, you MUST know the ratio of sides of the 30-60-90° as well as the 45-45-90° triangles, and you MUST...
July 11, 2016

math
incomplete question. Are you not getting any interest on your money?? in that case amount = 450 + 58.5w
July 11, 2016

math
Along the 12 ft length, the 6 inch tiles will fit exactly and you will need 24 along that side. Along the 14 ft side, you will need 28 tiles. total = 24(28) or 672 tiles or area = 168 square feet, but with 6 inch tiles, you will need 4 tiles per square inch total = 4(168) = ...
July 11, 2016

Math
and here is why ... pq - q = p+12 q(p - 1) = (p+12) q = (p+12)/(p-1) = 1 + 13/(p-1) clearly p > 1 , to have positive values for q to be an integer, 13/(p-1) has to be an integer, that is, p has to be either 2 or 14 so (2,14) or (14,2) e.g. if p = 2, q = 14 , Steve's ...
July 11, 2016

pre cal
I think you have a typo. Being familiar with these type of questions, it probably said: (x/x-1)^2 - (x/x+1) -2=0 if so, let y = x/(x-1) and carry on like I showed you in your previous post
July 11, 2016

pre cal
hint: let y = x^2, then your equation becomes 2y^2 - 5y + 2 = 0 carry on
July 11, 2016

mathematics
total = 36 students prob(boy) = 15/36 = 5/12
July 11, 2016

Pre Calculus
sum of sines: sinA + sinB = 2sin( (A+B)/2) cos( (A-B)/2) then: sin 150° + sin 30° = 2sin 90° cos 60° = 2(1)(1/2) = 1 Difference of sines: sinA - sinB = 2cos( (A+B)/2) sin( (A-B)/2) then: sin 4θ − sin 2θ = 2cos(3Ø)sin Ø
July 11, 2016

pre cal
let √x = y then: 2y^2 - 5y + 2 = 0 (2y -1)(y -2) = 0 y = 1/2 or y = 2 √x = 1/2 ----> x = 1/4 or √x = 2 ------> x = 4 or 2x+2 = 5√x square both sides: 4x^2 + 8x + 4 = 25x 4x^2 - 17x + 4 = 0 (x - 4)(4x - 1) =0 x = 4 or x = 1/4 btw, in both solutions...
July 11, 2016

Pre-Calculus 11
-3* cube root of 2 is a negative number, so your result has to stay negative. change it to - cuberoot(54)
July 10, 2016

math
just use for formulas for an AS term(n) = a + (n-1)d for yours a=22000 d=500 n=7 sum(n) = (n/2)(first + last) (you have the last term from above) or sum(n) = (n/2)(2a + (n-1)d )
July 10, 2016

Math
number of men --- m number of girls --- g m+g = 120 Tina danced with 7 men Reena danced with 8 men .... Raveena danced with 120-g men this is an arithmetic sequence with a=7, d=1 term(g) = m a + (g-1)d = m 7 + g-1 = m g - m = -6 also g+m = 120 add them 2g = 114 g = 57 m = 120-...
July 10, 2016

Math
construct your right-angled triangle. r^2 = x^2 + y^2 , (x is a side , not an angle) 2^2 = x^2 + 1^2 , since sinØ = opposite/hypoenuse or y/r x^2 = 3 x = √3 , we know the angle must be in Quad I sinx = 1/2 --- given cscx = 2 cosx = √3/2 secx = 2/√3 ...
July 10, 2016

Pre Calculus
5.4 radians coterminal with 5.4 - 2π = -.883.. radians, which is in the IV th or if you want to "think" in degrees 1 rad = 180/π ° 5.4 rad = 309.39.. ° ----> 4th
July 10, 2016

Pre Calculus
I did this yesterday http://www.jiskha.com/display.cgi?id=1468085862
July 10, 2016

mathematics
of the 40 oranges, 12 are unripe ----> 28 are ripe prob(ripe) = 28/40 = 7/10 so prob(unripe) = 1 - 7/10 = 3/10 you are correct
July 10, 2016

maths
nope , (x+y)^2=x^2+2xy+y^2
July 10, 2016

math
all the numbers that don't have a 5 in them: 8 x 9 = 72 , (they can start with 1,2,3,4,6,7,8,9 and they can end with 0,1,2,3,4,6,7,8,9 ) Those with a 5 are 100-72 = 28 prob(have a 5) = 28/100 = 7/25
July 10, 2016

math
smallest --- x middle one -- 2x largest ------ 3x x + 2x + 3x = 180 solve for x, sub back into my definitions
July 10, 2016

Pre-calculus
x = a(y-3)^2 + 0 but (4,9) lies on it, so 4 = a(9-3)^2 + 0 4 = 36a a = 1/9 x = (1/9)(y-3)^2 is your equation.
July 10, 2016

Pre-Calculus 11
is it (5/7)√(3/2) ? or 5/(7√(3/2) )?
July 9, 2016

math
3x-5y=16 -9x+15=48 notice that if you divide the 2nd by -3 , you get 3x - 5y = -16 clearly you will have two different parallel lines, thus no solution. or if we subtract: 3x-5y=16 3x-5y=-16 0 = 32 not very likely !!!! , so no solution
July 9, 2016

Mathematics
Memorize this relationship until you can state it in your sleep. π radians = 180° Use it to answer this, and your two previous questions.
July 9, 2016

Mathematics
repeatedly add 360° and note the results
July 9, 2016

Pre Calculus
You really really really MUST know that.
July 9, 2016

Mathematics
What is (2π - 11π/13) ? I get 15π/13 , which is not one of your choices. Do you have a typo?
July 9, 2016

Pre Calculus
same type of question as your last one
July 9, 2016

Pre Calculus
8π / 7= π + (1/7)π so just a bit more than π, so in quadrant III here is a "sneaky way" set your calculator to radians take sin 8π/7 to get a negative take cos 8π/7 to get a negative the only quadrant in which both sine and cosine are ...
July 9, 2016

Maths
Everybody studying trig should know the ratio of sides, and thus the trig ratios, of the 30-60-90° right angled triangles, as well as the 45 -45-90° triangle for the 30-60-90 the sides are 1 - √3 - 2 units respectively looking at your sketch of that triangle, ...
July 9, 2016

Spherical Trigonometry
h/100 = tan 38° solve for h
July 9, 2016

Calc.
I assume we are looking at vectors, then (6,2y) - (5x,10) = (6,-4) 6-5x = 6 , solve for x 2y - 10 = -4, solve for y
July 8, 2016

Calc.
⃗⃗u dot ⃗v =| ⃗⃗u| | ⃗v| cosØ, where Ø is the angle between them 2 + 20 + 2 = √21 √30 cosØ 24/(√630 =cosØ I get Ø = appr 17.02° check my arithmetic
July 8, 2016

Pre-Cal
I will do the 2nd one, which is the harder of the two. Follow my steps to do the first one. sinx = -5/13 ,and the angle x is in III recall that sinØ = y/r so y = -5, r = 13 sketch a right-angled triangle in III with hypotenuse 13 and y = -5 x^2 + y^2 = r^2 x^2 + 25 =169...
July 7, 2016

Raquel, check your answer - Algebra
Racquel, check your calculations. 2000(.08) + 8000(.09) = 880 , not 860 as needed.
July 7, 2016

Algebra
sue's rate = 1/60 (driveways/minute) Tom's rate = 1/35 (driveways/minute) combined rate = 1/60+1/35 = 19/420 (driveways/minute) time at combined rate = driveway/( (19/420) (driveways/minute) ) = 420/19 minutes = 22.1 minutes
July 7, 2016

pre cal
well, why don't you try expanding (x+s)^2 to see what comes out. btw, we use ^ to show exponents eg. x^2 is "x squared"
July 6, 2016

Math
Just translate the English using your definitions of a GS ar^3 = 30 ar^8 = 960 divide the 2nd by third, the a's will cancel r^5 = 32 r = 2 in ar^3 = 30 a(8) = 30 a = 15/4
July 6, 2016

pre cal
I will assume you meant: x^2/162 +x/18 + 1/9 = 0 the LCD is 162, so multiply each term by that x^2 + 9x + 18 = 0 (x+3)(x+6) = 0 x = -3 or x = -6
July 6, 2016

pre cal
number of twenties --- x number of tens ------- 3x 20x + 10(3x) = 1950 50x =1950 x = 39 so there are 39 twenties and 117 tens check: 39(20) + 117(10) = 1950
July 6, 2016

Pre Calculus
You really need help pushing buttons on your calculator???
July 6, 2016

Pre Calculus
form the half-life equation, amount = 69(1/2)^(t/12.4) , where t is in years plug in 75 for t show me your work and I will help you with the others.
July 6, 2016

lagdamat
What is "lagdamat" ?? width ----- x length ----- 2x+2 x(2x+2) = 24 2x^2 + 2x - 24 = - x^2 + x - 12 = 0 I will leave it up to you to solve this very simple quadratic. Hint1, it factors Hint2, reject the negative
July 6, 2016

math
What is (3/10)(2/7)(2905) ?
July 6, 2016

probability
I read that as a binomial distribution. so C(4,1) (1/2)^1 (1/2)^3 = 4(1/2)^4 = 1/4 or there are 2^4 or 16 cases your event could be HTTT THTT TTHT TTTH, or 4 possibilities prob(exactly one head) = 4/16 = 1/4
July 6, 2016

Analytic geometry
Name your points A(-8,8) and B(-2,2) So you want PA = 2PB Use you distance between points formula: √( (x+8)^2 + (y-8)^2 ) = 2√( (x+2)^2 + y-2)^2 ) square both sides (x+8)^2 + (y-8)^2 = 4( (x+2)^2 + y-2)^2 ) I will leave it up to you to expand and simplify the equation
July 6, 2016

math
Ahh, I see you fixed the problem from your earlier post. a) 20 men, 12 women, choose 5, with exactly 3 men = C(20,3) x C(12,2) = 2053(66) = 135498 b) at least 4 women ---> 4 women or 5 women = C(20,1) x C(12,4) + C(20,0) x C(12,5) = 20(495) + 1(792) = 10692 check my arithmetic
July 6, 2016

Math
Since the room is square, its side is √350 = 5√14 m your carpet is only 5√14 by 3√14 So clearly you will need an extra 2√14 m
July 6, 2016

math
your wording is gibberish. How can you have a committee of 5 people "if exactly three men must be on each committee and at least four women on each committee" Are there two different questions here?
July 5, 2016

Prealgebra
correct about the conversion to start. 3 m = 300 cm 2 m = 200 cm, (isn't the metric system great??) but 300/10.5 = 28.5 , so you will need 29 one way, and 200/10.5 = 19.04.. darn!, you will have to have 20 along the width So you will need 20x29 or 580 tiles. ( in reality ...
July 5, 2016

math
Area of ellipse = abπ where a and b are 1/2 of the axes respectively, that is, a = 7, b = 5
July 5, 2016

Pre Calculus
so you want: y = log3 (127) or 3^y = 1/27 , by definition of logs 3^y = 3^-3 y = -3 f(1/27) = -3
July 5, 2016

Pre Calculus
recall that ln 1 = 0 so x-3 = 1 x = 4
July 5, 2016

Pre Calculus
Where does the b come from in all your answers? Where does the 19 come from in all the answers? I suspect a typo
July 5, 2016

Math of investigation
Same post answered by Steve http://www.jiskha.com/display.cgi?id=1467634318
July 4, 2016

Pre-Calculus 11
∛5*5*5*3/4 = 5∛3/4 , assuming the 4 is not part of the cube root
July 4, 2016

Pre Calculus
I will try to show my synthetic division, the .... are spaces: 6+√6 | 1 ........ -11 ........ 18 ........ 32 .................... 6+√6 .... √6-24 .... -30 ............ 1 ..... √6-5 ..... √6-6 ........ 2 showing that: x^3-11x^2+18x+32 = (x-6-√...
July 4, 2016

maths
the time taken would be inversely proportional to the number of men, that is , the men we have working the less time it takes. t = k/m k = tm given: 8 men take 6 months k = 6x8 = 48 when m = 12 t = 48/12 = 4 or number of "man-months" = 48 time for 12 men = 48/12 = 4 ...
July 4, 2016

MATH
area of whole flag = 9000 cm^2 width of thin stripe --- x width of thicker stripe --- 2x area of stripes = 2x(90) + x(100) - 2x^2 ( we have to subtract the intersection of the stripes or else we would count it twice) = 280x - 2x^2 4500 = 280x - 2x^2 2x^2 - 280x + 4500 = 0 x^2...
July 4, 2016

math
You know how to find the area of a square if you know the sides, right? area = (5x+3y)^2 m^2 = (25x^2 + 30xy + 9y^2) m^2
July 4, 2016

math
which digits? at the left of what? at the right of what?
July 4, 2016

maths
unit digit --- x tens digit --- x+7 10(x+7) + x = 10(x + x+7) 10x + 70 = 20x + 70 10x = 0 x = 0 so the number is 70
July 4, 2016

maths
unit digit --- x tens digit -- 4x the number is 10(4x) + x or 41x the number reversed is 10x + 4x or 14x 41x - 14x = 54 27x = 54 x = 2 the original number is 82 check: 82-28 = 54 , all is good.
July 4, 2016

math
original number ---- x/(x+7) new number: (x+17)/(x+7-6) = (x+17)/(x+1) (x+17)/(x+1) = 2 2x + 2 = x+17 x = 15 the original number was 15/22
July 4, 2016

math
There are billions and billions of those. Some of them are: 3 and 5 6 and 10 30 and 50 5.4 and 9 6√3 and 10√3 -9 and -15 .... etc
July 4, 2016

Math
amount of original money ---- x (1/5)x + (1/4)(4/5)x + 360 = x x/5 + x/5 + 360 = x times 5, the LCD x + x + 1800 = 5x 3x = 1800 x = 600 check: he spent 1/5 of 600, or 120 , leaving him with 480 he spend 1/4 of 480 on food, leaving him with 360
July 4, 2016

Maths
V = (4/3)π r^3 dV/dt = 4π r^2 dr/dt when V = 2000 (4/3)πr^3 = 2000 r^3 = 1500/π r = (1500/π)^(1/3) = 7.8159... I stored in my calculator's memory so in dV/dt = 4π r^2 dr/dt 125 = 4π (7.8159...)^2 dr/dt dr/dt = .1628618 rate of change of ...
July 3, 2016

MATH
The hexagon is made up 6 equilateral triangles with sides of 9 ft Area of one of them = (1/2)(9)(9)sin60° = (81/2)(√3/2) = 81√3/4 area of whole hexagon = 6(81√3/4) = 243√3/2 area of whole hexagonal prism = 2(243√3/2) + 6(9)(6) = (243√3...
July 3, 2016

math
find the slope, then use the steps I showed you in your first post
July 3, 2016

math
Since your new line is parallel to the given line, it will differ only in the constant, so it will be -7x + 6y = c plug in the given point: -7(-1) + 6(-4) = c c = -17 new equation: -7x + 6y = -17 or 6y = 7x - 17 y = (7/6)x - 17/6
July 3, 2016

math
from what I had: y+6 = 8x + 40 y = 8x + 34 ---> this is correct standard form: 8x - y = -34 ---> this is correct general form: 8x - y + 34 = 0 ---> this is correct
July 3, 2016

math
y+6 = 8(x+5) I will leave it up to you to change it to the required form.
July 3, 2016

Math
let the amount of money be m let the number of people sharing be x let each persons share be y then xy = m second case: number of people = x+8 share of each person = y-1 then m = (x+8)(y-1) = xy + 8y - x - 8 thus: xy+8y-x-8 = xy x = 8y - 8 , where y > 0 , and y is a natural...
July 3, 2016

Math
If the new line is to be parallel to y = 4x +1, it will differ only in the constant, so let it be y = 4x + b, plug in the given point, find b, and you are done
July 3, 2016

math
bend = k mass given: 10 cm = k 4 kg k = 10/4 cm/kg or (5/2) cm/kg if mass = 7kg bend = (5/2)(7) = 17.5 cm
July 3, 2016

maths
let the total number be x (4/5)x are boys (1/5)x are girls, but (1/5)x = 100 x = 500 So we have 100 girls and 400 boys
July 3, 2016

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