Monday
December 22, 2014

Posts by Reiny


Total # Posts: 28,261

Introductory Algebra
Ummmh, isn't it about your school updated those old textbooks? France hasn't used the franc for years, they use the Euro.
June 11, 2014

algebra
cost of pound of copper ---- x cost of pound of tin -------- x+2 3(x + 2) + 7x = 10(3.85) 3x + 6 + 7x = 38.5 10x = 32.5 x = 3.25 copper sells for $3.25 per pound, and tin sells for $5.25 per pound
June 11, 2014

Math
I would write it as y = (8x^3)(3x-2)^(-1/2) and use the product rule dy/dx = (8x^3)(-1/2)(3x-2)^(-3/2) (3) + 24x^2 (3x-2)^(1/2) I will let you clean it up a bit
June 11, 2014

Math
yes, f(-6) = -18-5 = -23 f(4) = 12 - 5 = ........ f(8) = ........ range = { -23, ..... , .... }
June 11, 2014

trig
3secØ = 5 secØ = 5/3 then cosØ = 3/5 , since secA = 1/cosA Ø = arccos 3/5 = appr53.13° but you wanted the obtuse angle, so Ø = 360-53.13 = 306.87° , because the cosine is positive in quadrant I and IV to the nearest degree it would be...
June 11, 2014

Algebra
to get the y-intercept, let x = 0, that would leave you with y = 3 for the x-intercept, let y = 0 , that would leave you with x = 3 if the equation is of the form Ax + By = C do the same thing, usually you can do it your head e.g. 5x + 3y = 20 x-intercept is 4 y-intercept is 20/3
June 11, 2014

Algebra
of course
June 11, 2014

Algebra
treat it like two ordered pairs (1,295) and (2,272) slope = (272 - 295)/(2-1) = - 23 so equation in the form y = mx + b would be count = -23x + b , were x is the day number so using (1,295) 295 = -23(1) + b b = 318 count = -23x + 318 so on day 3 , x =3 count = -23(3) + 318 = ...
June 11, 2014

data management
a) z-score for 6 days = (6-7)/2 = -1/2 = -.5 b) go to your table at z = -.5 and find the corresponding probability , multiply by 8000 ( I got 2468 c) repeat the above for 4 days I found this website a great replacement for tables http://davidmlane.com/hyperstat/z_table.html
June 11, 2014

math (please check answer)
prob = (6/20)(2/19) = 3/95 you were right
June 11, 2014

algebra/what am I doing wrong Please help
You should have definitions for dependent, independent, and incosistent. if there is a unique solution , the system would be independent. since the two lines have different slopes, they MUST intersect in a point, thus independent Wolfram is great ... http://www.wolframalpha....
June 11, 2014

Please help me with this question.!!!!!!
I must admit that I had no idea what a "box and whisker" plot is, even though I taught math for 35 years, so I looked it up and found this video of the very useful Khan Academy by Sal Khan https://www.khanacademy.org/math/probability/descriptive-statistics/Box-and-...
June 10, 2014

Algebra
prob on base = .45 prob not on base = .55 prob (on base 5 of 7 times) =C(7,5) (.45^5)(.55^2) = appr .117
June 10, 2014

Math
-4x-8>4 -4x > 12 divide both sides by -4 x < -3 You add and subtract jus like you would for an equation, but when you divide by a negative, like I did in the last step, you MUST reverse the inequality sign.
June 10, 2014

math (cant figure it out)
Prob(vowed, then Q) = (3/6)(1/6) = 3/36 = 1/12 How did you possible get 1/10 ?
June 10, 2014

math *check*
Strike 2 prob (red from 1st then red from 2nd) = (12/20)(8/13) = 24/65
June 10, 2014

algebra
what is 4^3 - 5(4^2) + 4 ?
June 10, 2014

math
1/8 = .125 or 12.5% so to double we would solve 1(1.125)^n = 2 log both sides log (1.125^n = log2 n log 1.125 = log2 n = log2/log 1.125 = appr 5.885 years for tripling, solve 1.125^n = 3 ------> you should get appr 9.33
June 10, 2014

math *check*
prob(green) = 9/20 prob(not green) = 11/20 odds in favour of green = (9/20) : (11/20) = 9: 11 you are correct.
June 10, 2014

math (cant figure it out)
Valid point by Writeacher, if they they are numbered from 0-10 , there would be 11 sections. Clarify before I answer it.
June 10, 2014

math
strange wording .... " Finding three geometrically numbers" I assume you have 3 numbers in a geometric sequence. "30 units exceeds the sum of the other two" ...... which "other two" , the first two, the last two , or the middle two ? the three ...
June 10, 2014

Math
Use Cartesian geometry let the first be at (1,120) and the last one at (7,12) slope = (120-12)/(1-7) = -18 so for each increase in x, the height drops 18 cm so you want two decreases, height of third = 120-2(18) = 84 or find the equation: y = -18x + b at (7,12) 12 = -18(7) + b...
June 10, 2014

math -interest
i = .14/12 = .0116666... n = 12 400 = payment (1 - 1.011666...^-12)/.01166.. I get payment = 35.91
June 10, 2014

Algebra 1
y = x^2 - 4x+ 4 = (x - 2)^2 for x-intercept, let y = 0 (x-2)^2 = 0 x-2 = 0 x = 2 we have a double root at x = 2 , ( x=2 or x=2) see Wolfram: http://www.wolframalpha.com/input/?i=plot+y+%3D+x%5E2+-+4x+%2B+4 Usually , I would put my money on Wolfram.
June 10, 2014

math
If f(x) will "vanish" when x = 1 and x = -2 (x-1) and (x+2) must be factors assume we have f(x) = a(x+b)(x-1)(x+2) given: f(-1) = 4 ---> 4 = a(-1+b)(-2)(1) -2a(-1+b) = 4 2a - 2ab = 4 a - ab = 2 f(2) = 28 ---> 28 = a(2+b)(1)(4) 4a(2+b) = 28 8a + 4ab = 28 2a + ab...
June 10, 2014

math
I see about 9 questions that you posted all dealing with the factor and remainder theorems. You have shown no effort on your part or let us know where you difficulties are. They all basically follow these two concepts : if for some f(x) , x-a is a factor, then f(a) = 0 if for ...
June 10, 2014

math
p(4) = 64k + 48 - 3 = 64k + 45 Q(4) = 128 - 20 + k = k + 108 by the remainder theorem , each of these are the remainders when divided by x-4 But they are equal ... 64k + 45 = k + 108 63k = 63 k = 1
June 10, 2014

math
x^3-a^2x+x+2 is divisible by x-a so x=a has to give a result of 0 when subbed in a^3 - a^2 (a) + a + 2 = 0 a^3 - a^3 + a + 2 = 0 a = -2
June 10, 2014

maths
area = (4)(6)sin52° = ....
June 10, 2014

check answer
good, carry on
June 9, 2014

algebra
g^-1 = { (5,-4), (2,3), (0,4)} h^-1(x) = (x-9)/2 g^-1 (2) = 3 h^-1 (x) = (x-9)/2 (h*h^1) (-7) .... is there a typo? did you mean (h*h^-1) (-7) ?? if so, then (h*h^-1) (x) = (2x+9)(x-9)/2 = (2x^2 + 9x - 81)/2 (h*h^-1) (-7) = (98 - 63 - 81)/2 = -23
June 9, 2014

Math
Basic property of triangles: the largest side is opposite the largest angle the smallest side is opposite the smallest angle etc since angle A is 125° , the sum of the other two angles must be 55° that is, "a" must be the largest side, but b > a which ...
June 9, 2014

Precalculus
Expected pay-out = .04(300) + .03(400) + (.03)(.04)(6000) = 12 + 12 + 7.20 = $31.20 how did you get 31.40 ? to make a $10 profit, they should charge 41.20 per policy
June 9, 2014

Algebra 1--Please, help me!
1. for the x-intercept let y = 0 ---> x = 2/3 for the y-intercept , let x = 0 ---> y = -2 2. (3m^2 n)/(5m)(20mn/n^6) = (3mn/5)(20m/n^5) = 12m^2/n^4 ------> a) 3. 3/x + 3/(5x) LCD = 5x = 15/(5x( + 3/(5x) = 18/(5x)-----> c)
June 9, 2014

Algebra
domain: { -7,9,0} range : { 5,-4,3,-7}
June 9, 2014

Algebra 1--Please, check my answer!
1. the slope of x+2y = -6 is -1/2 so we are looking for a line with slope +2 so anything starting with 2x-y = .... or -2x + y = ... will do. looks like b) to me 2. They all factor and simplify a) 3(x+2)/((x+2)(x-1)) = 3/(x-1) , x ≠ -2 b) 3(x-1)/((x-1)(x-1)) = 3/(x-1) , x...
June 9, 2014

algebra/can you show me how to solve problem
f(x) = x^2 + 2 f(-3) = (-3)^2 + 2 = 9+2 = 11 notice that I substituted x with the given value of x wherever I saw an x do the others the same way
June 9, 2014

Algebra 1--Please, help me!
see later post
June 9, 2014

Algebracan you answer my question
http://www.wolframalpha.com/input/?i=plot+x-y%3D4+%2C+2x%2B3y%3D13+
June 9, 2014

Math
let y = -x^2 + 5x + 5 dy/dx = -2x + 5 = 0 for a max of y 2x = 5 x = 5/2 when x = 5/2 y = -25/4 + 5(5/2) + 5 = 45/4 you should recognize y = -x^2 + 5x + 5 as a downward opening parabola , the max is 45/4 when x = 5/2
June 9, 2014

Calculus
if f ' (x) = 2x- 3x^2 f(x) = x^2 - x^3 + c f(0) = 0-0+c f(3) = 9 + 27 + c = 36+c change from f(0) to f(3) = 36+c - c = 36
June 9, 2014

algebra
Your expansion is incorrect 3(x-5)(x+5) = 3(x^2 - 25) = 3x^2 - 75 Since you wanted a quadratic equation, it should be 3x^2 - 75 = 0
June 9, 2014

algebra
What did you get ?
June 9, 2014

Algebra
follow the same steps that I showed you in your previous post of the identical type of question. It appears you never even looked at it.
June 9, 2014

Algebra
that would simply be f(x) = 2(x+3)(x+4) = 2x^2 + 14x + 24
June 9, 2014

Math
1by1 --- 64 of them 2by2 --- 49 3by3 --- 36 4by4 --- 25 5by5 --- 16 6by ----- 9 7by7 ---- 4 8by8 ---- 1 total = 204 There can only be an equal number of reds and blacks in the even-numbered squares, so 64 + 36 + 16 + 4 + 1 = 121 121 blocks have the same number of reds and ...
June 9, 2014

Probability!
since you are replacing the marble, the second draw is not affected by anything you did before. so Prob(red, then blue) = (8/43)(12/43) = 96/1849
June 9, 2014

MATH
correct
June 9, 2014

MATH
For the first, the following are divisible by 3: 3 6 9 so what do you think?
June 9, 2014

math.
0 < (x+3)/2 < 5 multiply by 2 0 < x + 3 < 10 subtract 3 -3 < x < 7
June 9, 2014

Algebra
I think the main purpose of the question, even though they did not say that, was to show that the midpoint of the hypotenuse is equidistant from the 3 vertices. All I did with the slope calculation was to show that the triangle is indeed right-angled. Other than that, finding ...
June 9, 2014

Algebra
I don't understand your question. I DID use the distance between two points formula, I just did not show the subtraction since that is easily done in your head. here is one of them with all steps : AM = √( 2.5 - 1)^2 + (3.5-1)^2 ) = √( 1.5^2 + 2.5^2) = √2...
June 9, 2014

Algebra
Your diagram should show that you have a right angle at B , but let's prove it anyway. slope AB = (2-1)/(5-1) = 1/4 slope of BC = (6-2)/(4-5) = -4 YES, AB is perpendicular to BC, thus AC is a hypotenuse midpoint of AC = M( (1+4)/2 , (1+6)/2) = M(5/2 , 7/2) = M(2.5 , 3/5) ...
June 9, 2014

Algebra
(f*g)(x) = (2x+5)(x^2 - 3) = 2x^3 + 5x^2 - 6x - 15 do the other one in the same way
June 9, 2014

trig
let's fit the data to a curve of the type f(t) = a cos k(t +d) + c from highest to lowest = 65-25= 40 cm so a = 20 from highest to lowest = .3 s to 1.8 s so period = 3 seconds 2π/k = 3 k = 2π/3 so far we have f(t) = 20 cos (2π/3) (t +d) + c let's raise ...
June 9, 2014

Maths, Divine International Public School
cotA = 8/15 tanA = 15/8 so y=15, x=8 r^2 = 15^2 + 8^2 r = √289 = 17 sinA = 15/17 cosA = 8/17 then (1+SinA)(1-SinA)/(1+CosA)(1-CosA) = (1 - sin^2 A)/(1 - cos^2 A) = (1 - 225/289)/(1 - 64/289) = (64/289) / (225/289) = 64/225
June 8, 2014

Math
upwards: f(x) = (x+2)(2x+5) downwards f(x) = -(x+2)(2x+5) expand if needed
June 8, 2014

Math 11
I hope you made a diagram. label the window position P label the top of the statue T label the bottom of the statue B So we want TB I can find BP sin34° = 20/BP BP = 20/sin34 let's use the sine law in triangle TBP TB/sin4 = BP/sin120 TB = BPsin4/sin120 = (20/sin34)(...
June 8, 2014

Math helpppp!
You gave the equation in vertex form so the vertex is easily read to be (6,3) for standard form, just expand your function h(x) = x^2 -12x + 36 + 3 = x^2 - 12x + 39
June 8, 2014

math
Euler said: V + F - E = 2 so if 4 + 6 - E = 2 -E = -8 E = 8 It has 8 edges
June 8, 2014

math
This is the same as finding a Lowest Common Denominator 20 = 2*2*5 24 = 2*2*2*3 30 = 2*3*5 so we need: 2*2*2*3*5 or 120
June 8, 2014

math
let a^(2/3) = y for easier typing then x = y - 1/y = (y^2 - 1)/y x^3 = (y^6 -3y^4 + 3y^2 - 1) / y^3 = (a^4 - 3a^(8/3) + 3a^(4/3) - 1)/a^2 or a^2 - 3a^(2/3) + 3a^(-2/3) - a^-2 3x = 3a^(2/3) - 3a^(-2/3)
June 8, 2014

math
present age: michael ---- x max ------- x-5 4 years ago: michael ---- x-4 max ------- x - 9 x-4 + x-9 = 25 2x = 38 x = 19 Michael is now 19 , and Max is now 14 check: 4 years ago , Michael was 15 and Max was 10 was the sum of their ages at that time 25? YES
June 8, 2014

Math
The equation for your cost: cost = .1(m-500) + 25 , where m is in minutes so : .1(m-500) + 25 > 30 For the second part, m = 525 cost = .1(525-500) + 25 = $27.50
June 8, 2014

Pre-Calc
For any (r,Ø) x = rcosØ, y = rsinØ so x = 5cos(π/4) , y = 5sin(π/4) x = 5√2/2 , y = 5√2/2 so you have the point (5√2/2 , 5√2/2) (I don't see why you would want to write that in decimals, since you have to round it) ...
June 7, 2014

Algebra confused/Thank you
You should be able to read the solution. http://www.wolframalpha.com/input/?i=plot+3x+%2B+2y+%3D+5+%2C+4x+−+3y+%3D+1
June 7, 2014

maths
a+bi = √(1+i)/√(1-i) = √(1+i)/√(1-i) * √(1-i)/√(1-i) = √(1 - i^2) / (1-i) = √(1 - i^2) / (1-i) * (1+i)/(1+i) = √2(1+i)/2 = √2/2 + √2/2 i so a = √2/2 and b=√2/2 and a^2 + b^2 = 2/4 + 2/4 = 1
June 6, 2014

Algebra
Put Hobbinton at the origin (0,0) on the x-y grid then Tom's house would be (12,-16) distance from (0,0) to (12,-16) = √(12^2 + (-16)^2) = √400 = 20
June 6, 2014

math
prob(c) = 1/4 prob(not c) = 3/4 so you are looking for c c notc = (1/4)(1/4)(3/4) = 3/64 c notc c = (1/4)(3/4)(1/4) = 3/64 notc c c = (3/4)(1/4)(1/4) = 3/64 prob of your event = 3(3/64) = 9/64
June 6, 2014

Algebra
the way you typed it, there is very little simplification I multiplied top and bottom by x^2 to get (x^3 + 3 - 36x + 3x^2)/(x^3 + 3x^2) , and that's about it. If you meant: ( (x+3/x^2 -36/(x+3)) /( (x+3)/x ) it would be something totally different. I can't guess what ...
June 5, 2014

MATH
Pick any x say, x = 0 y = 2(0)-5 = -5 ----> the point (0,-5) how about x = 4 , (or any x you feel like) then y = 2(4) - 5 = 3 --- the point (4,3) plot (0,-5) and (4,3) , join the with a straight line, extend the line to any length you feel like
June 5, 2014

math
that would be 8 - choose - 4 = C(8,4) = 8!/(4!4!) = 70
June 5, 2014

trig
For your first one, You should recognize those numbers as belonging to the 30-60-90° right-angled triangle which would make c = 1 If you didn't notice that, you could use the cosine law c^2 = 2^2 + √3^2 - 2(2)(√)cos30° = 4 + 3 - 4(√3)(√3/2...
June 5, 2014

math word problems
original: x by x area = x^2 new dimensions: (x+3) and (x+2) new area = (x+3)(x+2) = x^2 + 5x + 6 x^2 + 5x + 6 - x^2 = 46 5x = 40 x = 8 original was 8 by 8 check: old area = 64 new is 11 by 10 new area = 110 change in area = 110-64 = 46 , yeahh!
June 4, 2014

Precalculus
#3 Those are permutations since the order matters a) start with a vowel: 2*5*4 = 40 , you were right b) all consonants, means we only pick from 4 4*3*2 = 24 , you were right c) all vowels, you are right with 0 since we only have 2 vowels and we need 3 d) all consonants , ...
June 4, 2014

Math - Business Calc.
I noticed an error in Damon's solution 4th line : V = (17-2h)(5-2h)h = (17-h)(5h-2h^2) should be : V = (17-2h)(5-2h)h = (17-2h)(5h-2h^2) I had h = 1.1445
June 4, 2014

Algebra - Help!!
I did a synthetic division of x^3 - 7x + 6 by x+3 to get the other dimension of x^2 - 3x + 2 , looks like a)
June 4, 2014

Math
Where is the second equation ?
June 3, 2014

algebra math
so she need one of 10, 11, or 12 prob of that = 3/12 = 1/4
June 3, 2014

Algebra
LCD is 24x -9y/(12x) + 28y/(12x) - 2y/(12x) = 17y/(12x)
June 3, 2014

Math
x^3 - x^2 - x + 8 = 0 tough one - it does not factor tried x = ±1, ±2, ±4 , none worked so no rational root what about real roots? let f(x) = x^3 - x^2 - x + 8 for f(-1) = -1 -1 +1 +8 = 7 for f(-2) = -8 - 4 + 2 + 8 = -2 so there is a real root between -2 ...
June 3, 2014

math
Did you make a sketch? I have a right-angled triangle with a base of 15 and a height of 4, (10 ft - his 6 ft) so in relation to your angle of elevation Ø, we have the opposite and the adjacent, suggesting tanØ = 4/15 arctan = 14.93° So to the nearest degree: ...
June 3, 2014

math
PV = 25000(1.03)^-28 = $10,926.92 i = .12/4 = .03 n = 7(4) = 28
June 3, 2014

Math
the above factor of x^3 - 1 factors to (x-1)(x^2 + x + 1) the x-1 = 0 gave us x = 1 x^2 + x + 1 = 0 x = (-1 ±√-3)/2 or x = (-1 ± i√3)/2
June 3, 2014

Math
5x^4=5x x^4 - x = 0 x(x^3 - 1) = 0 x = 0 or x^3 = 1 x = 0 or x = 1 There are also two complex roots, but I don't think you have studied that. Let me know if you did.
June 3, 2014

math
second question: How can Frank be a jacket ? third question: What language is this: "what is the fraction of the amount that he that he needs to saved" What does that mean?
June 3, 2014

math 1 question!!!!!!
Didn't Ms Sue just prove to you that is is C ??
June 3, 2014

correction - math
subtract them as they sit -y = 4 y = -4 back into the first: x -3(-4) = 25 x + 12 = 25 x = 13 x = 13, y = -4 , you had them opposite.
June 3, 2014

Math
correct
June 3, 2014

Math
adults --- x girls ----- 4x boys ------5x (note x: 4x : 5x = 1 : 4 : 5) "6 more boys than girls" ---> 5x = 4x+6 x = 6 so we had 6 adults, 24 girls, and 30 boys, (satisfying all our conditions stated)
June 3, 2014

Math
nope f(-3) = (-3)^2 - 5(-3) + 1 = 9 + 15 + 1 = 25
June 3, 2014

If 12 people are playing in a tournament and?
number of subsets of 2 elements from a sample space of 12 = C(12,2) = 66
June 3, 2014

Math
yes
June 3, 2014

Math
f(4) = 16+9 = 25 g(-1) = 24-4 = 20 so what is the problem?
June 3, 2014

Math ~ Check Answers ~
use the first pair of points (2,1) and (4,0) slope = -1/2 so y = mx + b ----> y = -(1/2)x + b sub in (4,0) 0 = (-1/2)(4) + b b = 2 y = (-1/2)x + 2 use our non-used point to check: does (6,-1) lie on it? LS = -1 RS = (-1/2)(6) + 2 = -3+2 = -1 your answer is good.
June 3, 2014

Algebra 1--Please, help me!
((n-5)/(n^2 - 2n -3)) / ((n-3)/(n^2 -4n - 5)) multiply both sides by (n^2 - 2n -3)(n^2 - 4n - 5) , sometimes called cross-multiplying n^3 - 4n^2 - 5n - 2n^2+ 8n + 10 = n^3 - 2n^2 - 3n - 3n^2 + 6n + 9 -n^2 = -1 n^2 = 1 n = ± 1
June 3, 2014

word problem?
prob(going to amusement park) = 8/18 = 4/9 so number of the 225 who would go = (4/9)(225) = 100 notice Ms Sue's equation will yield the same answer.
June 3, 2014

Algebra 1
did that for you here http://www.jiskha.com/display.cgi?id=1401816411 #2, was also done somewhere, can't find it, so ... The way you typed it: 2/t + 4/3t = 4/t + 2 times 3t 6 + 4t^2 = 12 + 6t 4^2 - 6t - 6 = 0 2t^2 - 3t - 3 = 0 t = (3 ± √33)/4 somehow I don'...
June 3, 2014

Scientific notation
area = (5x10^4)(6x10^3) = 30x10^7 = 3.0 x 10^8 m^2
June 3, 2014

Probability???
yes, but I would rather have you think of (1/520)(7800) = 7800/520 ---> see, there is your division by 520 = 15
June 3, 2014

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