# Posts by Reiny

Total # Posts: 39,546

Math
Ruby now ---- x Pawan now --- 2x 3 years ago: Ruby --- x-3 Pawan -- 2x-3 2x-3 = 3(x-3) carry on

Algebra
Rider: y = .5x + 50 UMove: y = .75x + 45 Just follow the instructions, they are quite clear.

Math
solve: x^3 + 3x + 1 = -3 x^3 + 3x + 4 = 0 let x = 1 ---> 1+3+4 = 0 ? no let x = -1 ---> -1-3+4 = 0 , yeahh x^3 + 3x + 4 = (x+1)(x^2 - x + 4) = 0 so x=-1 or x is a complex number so f^-1 (-3) = -1 check: f(x) = y = x^3 + 3x + 1 f(-1) = -1 -3 + 1 = -3 the inverse is: x = y...

Math
and a rhombus

pre-algebra
1. It said: "The length of a yard is triple the length of the garden" --> so if you let the length of the garden be x then the length of the yard is 3x (we could have used any variable name, you used G, that's fine) It said: "the difference between the ...

Calculus (RATE OF CHANGE)
Make a sketch and use the cosine law: let the rate of the slower car be x mph then the rate of faster car is 2x mph Let the distance covered by the slower car by x then the distance covered by the faster car is 2x let the distance between them be d d^2 = x^2 + 4x^2 -2x(2x)...

Calculus (RATE OF CHANGE)
I assume you want dy/dx y = 1/x + 2 dy/dx = -1/x^2 when x = 2 dy/dx = -1/4

Math
I think you have a typo. You want a 6th added, so there should have been 5 of them given already. You only have four of them

Calculus
see my previous reply, in this case multiply each term by 7, then go from there

Calculus
Some authors consider 18x + y = 13 to be "standard" form , and 18x + y - 13 = 0 to be "general" form Look at your text or notes

calculus
Are there supposed to be exponents in your equation?? I will assume: V = ?aT^3 + bT^2 ? cT + 1 , using the given: dV/dT = -3a T^2 + 2b T - c I assume you plugged in the given values for a, b, and c, used the quadratic equation formula and solved for T Since the coefficient of ...

pre-algebra
number of votes for Michael --- M number of votes for Tina = M - 200 number of votes for Sam = M + 4200 (you had that, good!) Now, just translate: "Samantha plus the number of votes received by Michael minus the number of votes received by Tina (M + 4200) + M - (M-200) = ...

Algebra
You should define your variables, hard to check without knowing what x stands for e.g. let the "other " angle be x then "one" angle is 4x+2 "The third angle is three times the first angle decreased by 6" ---> poor wording. How do we know which ...

Math
certainly not linear, slopes between pairs of points would have to be the same, --- they are not. Took differences in the y values up to the fourth difference columns. No constant so , no polynomial up to 4th degree. Not even Wolfram found an equation, when to least-fit ...

Math, data management
no, you probably meant 10!/(4!,3!,3!) = 4200

Algebra
see http://www.jiskha.com/display.cgi?id=1487716112 this is very similar, except you would have 1/x and 1/2x as the combined rate, and you know that result.

Algebra
look at the solution both Damon and I gave here for a similar question http://www.jiskha.com/display.cgi?id=1487716112 The only difference is that here you are given the combined rate.

Math - Calculus
Make a sketch. Your rock will travel in a circle whose equation is x^2 + y^2= 9 you must release it at a point P(x,y) so that it reaches a point (15,0) Anyway, we have right-angled triangle , (at the point of release, the angle is 90° between radius and tangent. let the ...

Algebra
rate of old machine = 1/170 rate of new machine = 1/119 combined rate = 1/170 + 1/119 time at combined rate = 1/(1/170+1/119) = 1/(1/70) = 70 minutes

Algebra
one number --- x the other ------ x-32 1/(x-32) + 5(1/x) = 1/6 times 6x(x-32) 6x + 30(x-32) = x(x-32) 6x + 30x - 960 = x^2 - 32x x^2 - 68x + 960 = 0 (x-20)(x-48) = 0 x = 20 or x = 48 if x = 20 then the other is negative, but both our numbers are to be positive so x = 48 and ...

Math
v = -32t + 28 Is there a question?

*** Monitor Needed For Banning
Mehdi Moustaoui

algebra
x(500) = .1(200) + .2(300) x = 80/500= .16 change my answer to a percent.

Math
we can find the equation of the line, you have the slope and a given point. Once you have the equation, replace the x with anything you want, then find its matching y value

Algebra
3.18x+2.6+0.9x+x=28 5.08x = 24.4 x = 24.4/5.08 = 5 Hali's equation of 5.1x = 25.4 -->(no idea where that came from ) does not yield the solution of x = 5 as he concluded.

Math
This looks like an assignment or test. I don't see your choices for the answers nor any indication where you had difficulty. You weren't expecting somebody to just do this for you, did you ?

kishore
originial fraction ---- a/b case 1: (a+1)/(b+3) = 1/2 2a +2 = b+3 ----> 2a - b = 1 or b = 2a-1 case 2: (a-1)/(b+2) = 2/5 5a - 5 = 2b+4 5a - 2b = 9 use substitution: 5a - 2(2a-1) = 9 a = 7 , then b = 13 the original fraction was 7/13

math
your height equation must be h = -4.5t^2 + 25t + 50 so you want to solve: 7 = -4.5t^2 + 25t + 50 4.5t^2 - 25t - 43 = 0 use the quadratic formula, discard any negative value of t

Mathematics
What is 1 - (.9)^5 ?

math
right now: 40 people signed up, \$120 per person. let the number of additional skiers be m number going : 40+m cost per skier : 120-2m revenue = (40+m)(120-2m) = 4800 + 40m - 2m^2 This is a quadratic, a parabola opens down, so it has a maximum revenue. This is found by finding ...

Maths
I will assume compound interest, i = .06/12 = .005 amount = 12000(1.005)^42 = .... subtract the original 12,000 to find the interest. for interest earned after 2 years = 12000(1.005)^24 - 12000 "How much interest is earned each year " - this would require 42 ...

Math
I made a sketch on a grid, I labeled the point at the anchor (0,2) and the point of atachment at the pole as (x,45) (45-2)/(x-0) = 3/5 3x = 215 x = 215/3 Now , use the formula for the distance between 2 points

Algebra
Your equation should have been 25y^2 - 60y + 324 = 0 by the formula: y = (60 ±?-28800)/50 = (60 ± 120?-2)/50 = (6 ± 12i?2)/5 which is a complex number

maths
speed at remaining distance ---- x km/h (2/3)(450)/75 + (1/3)(450)/x = 13/2 300/75 + 150/x = 13/2 times 2x 8x + 300 = 13x carry on

math
I agree with Bosnian's answer. check your typing of the question. Did you perhaps mean ?15/(9y) < 11/13 ?

Math
At the moment she steps off, her linear velocity equals the rate the arc length is increasing. circumference = 2?(25) = 50? ft 36° = 36/360 = 1/10 of a rotation so the linear velocity of any point is 5? ft/second 5? ft/1 second = (5?/5280) / (1/3600) miles/hour = (5?/(5280...

Algebra
So I assume it is 4x^3 = 16 then: 4x^3 - 16x = 0 4x(x^2 - 4) = 0 4x(x+2)(x-2) = 0 x - 0, ± 2

MATH (POST 2) Need Help Please
I am not familiar with the "average daily balance method " , I don't live in the US. Perhaps one of the other math tutors can help out here.

Algebra
Apparently we are supposed to ignore the loss due to saw-cuts, a bad idea. Looks like we have two verticals and 3 horizontal pieces. let each of the verticals be x and each of the horizontals be y 2x + 3y = 72 inches y = (72-2x)/3 volume = 24(x)(y) = 24x(72-2x)/3 = 576x - 16x^...

Algebra
length ---- x width ----- y 2x+2y = 42 x+y = 21 y = 21 - x printing area: length = x-2 width = y-3 = 21-x - 3 = 18-x area = (x-2)(18-x) = 18x - x^2 - 36 + 2x = -x^2 + 20x - 36 since this is a downwards parabola, the vertex will be the answer to your question. Find the vertex ...

Math
"Guessing" ??? Good grief, this is math. \$8 to rent a car for 15 days ????? just plug in your data .... C = 50(15) + .15(475) = ......... I am sure you have a calculator if you can't do it with pencil and paper.

math
(x/50)+(x/25)+(3x/50)+(2x/25)+...+2x = x/50 + 2x/50 + 3x/50 + 4x/50 + ... 100x/50 = (x/50)( 1+2+3+4+ ... + 100) continue

math
slower speed ---- x km/h faster speed ----- x+6 km/h 5x + 4(x+6) = 294 easy to solve....

math
(4xy+2xy)^2 did you notice that you have like terms, so = (6xy)^2 = 36 x^2 y^2

math
P(A or B) = P(A) + P(B) - P(A and B) your data fits that formula

@ penny - math
Penny, it is you who determines if you fail or pass, please don't blame Steve.

Math
Use your formulas ar = -6 ar^4 = 48 divide them: r^3 = -8 r = -2 now find a, then use the formula for the sum(n) terms let me know what you get, so I can check it

math
How many 5's do you see on 1 die ??

Algerba
Well, why don't we solve it, probably faster than subbing in all those values -1.5^2+4x+2.2=0 3x^2 - 8x - 4.4 = 0 x = (8 ± ?116.8)/6 = appr 3.13 or -.5 you are right

maths
list the first prime numbers, add them up, then divide by 10 remember the first prime number is 2, then 3, etc

Algebra I
4p - 2m = 2 ---> 2p - m = 1 or m = 2p-1 3p + 9m = 54 sub in m=2p-1 into the other equation and solve

math
how many kings ? how many hearts ? remember not to count the king of hearts twice, it would be included in both counts.

maths
so you have 2/5 left (2/5)x = 80 2x = 400 x = 200 check: take 3/5 of 200 and subtract it from 200. What do you have left ?

@ Steve - MATH
Nice!!! Well, I always like to take those long detours. I once went from Toronto to Niagara Falls by going all the way around Lake Ontario.

MATH
cos 4A = cos^2 2A - sin^2 2A = (cos 2A - sin 2A)(cos 2A + sin 2A) = (cos^2 A - sin^2 A - 2sinAcosA)(cos^2 A - sin^2 A + 2sinAcosA) from cosA = 1/2 ----> sinA = ?3/2 (A = 60° or ?/3) plug the cos and sin values into my last equation and evaluate, I will leave the ...

math
(1/3)p = 2 p = 6

Geography
The angle between is 150° which is 150/360 or 5/12 of a rotation. 5/12 of 24 hours is 10 hours. so the time would be 5:30 - 5:00 = 19:30 ---> evening of previous day ( that would be 7:30 pm using US notation) time decreases from east to west

algebra 2
my starting equation would be: y-5 = -1(x+3) re-arrange it to see which one fits

Algebra 1
What makes you "think" it is either a or c What did you do to get the answer?

algebra
What are you doing ???? (4275)(4372) = 18,690,300

math
your number ---- x x/4 + 5 - 6 = 6 x/4 = 7 multiply both sides by 7 x = 28 try it.

math
I think that should be 48 done 6 years ago by MathMate http://www.jiskha.com/display.cgi?id=1307634385

math
you have posted 4 disconnected statements 215 = 0.73n ----> false n = 0.73 × 215 ----> does not follow from the previous, but would be correct 0.73 = n × 215 -----> does not follow from the previous 215 = 73n ---> does not follow the previous, but ...

Math
suppose we use an example: e.g. f(x) = (x-5)^2 + 3 , which is a parabola with vertex (5,3), opening upwards f(2-x) = (2-x - 5)^2 + 3 f(2-x) = (-x - 3)^2 + 3 f(2-x) = (x+3)^2 + 3 , (just like (-9)^2 = 9^2 ) -f(2-x) = -(x+3)^2 - 3 so we have a reflection in the x-axis, and a ...

Math
let the length be x let the breadth be y perimeter = 2x + 2y given : length : perimeter = x : 2x+2y = 1:3 x/(2x+2y) = 1/3 3x = 2x+2y x = 2y length : breadth = x : y = 2y:y = 2 : 1

Maths
The way you typed it, ?h^2 would simply be h Is that what you want or did you mean: A=?r?(h²-r²) -----> critical brackets I will wait for your reply

math
Just noticed that Steve answered the same question 3 years ago, when it was stated as a complete question http://www.jiskha.com/display.cgi?id=1392441787

math
So ?

math
place 1 on its place on a number line, now count 15 to the right, then 15 to the left I get 16 with1 and -14 with 1 how far from 1 to 16 ? how far from -14 to 1 ?

Mathematics
Assuming that "bearing" to you means North = 0 and you are going clockwise. Make a sketch and complete the right-angled triangle: sin20° = y/50 ---> y = 50sin20 = appr 17.1 km or cos70° = y/50 ---> y = 50cos70 = appr 17.1 km

Maths
Let's compare the value of \$1 at the end of 10 years at both types of interest: compound: Value = 1(1.06)^10 simple: let the rate be r interest = 1(10)(r) = 10r value = 1 + 10r so 1 + 10r = 1.06^10 10r = 1.790847... - 1 r = .0790847... rate = 7.91% to 2 decimals

Math
the general term of an AS is a + (n-1)d, where a is the first term, d is the common difference, and n is the number of terms so : a = 0 a+9d = 15 0+9d = 15 d = 15/9 = 5/3 For 10 to be one of the terms a + (n-1)d = 10 0 + (n-1)(5/3) = 10 times 3: 5(n-1) = 30 5n-5 = 30 5n = 35 n...

Algebra
(x-1/2)-(x-2/2)+(x-3/2)-...-(x-100/2) = x - 1/2 - x + 2/2 + x - 3/2 - .... - x + 100/2 = x-x+x-x+x-....-x -1/2 + 2/2 - 3/2 - ... + 100/2 looking at the last term, we see there are 100 terms, so the x's drop out = -1/2 + 2/2 - 3/2 - ... + 100/2 = (-1/2)(1 - 2 + 3 - .... + ...

You are correct at 36/7 another way to look at it: there are 12 half-hours in 6 hours. Have Katie look at a clock. So the length is 12*(6/7) = 36/7 inches

Math
In your trig repertoire , you should know the 3 basic trig values of angles 0°, 30°, 45°, 60°, 90° by knowing the ratio of sides of the 30-60-90 and the 45-45-90 degree triangles. This is very very important in any further study of trig. I will do the only...

Math
FG----> 25+6.5n, where n is the number of games GB ---> 57 + 2.5n 25 + 6.5n = 57 + 2.5n 6.5n - 2.5n = 57 - 25 carry on

Math
hint: sure looks like the coach is collecting \$22 from each player. So on Friday, he collects from 2 players, or \$ .....? So from p players, he collects \$ .... ?

Math Help
The order does not matter, so this is a "combination" problem Number of possible 4 cards from the reds = C(26,4) or 26!/(22!4!) number of possible 4 cards from all = C(52,4) or 52!/(48!4!) prob(your event = C(26,4)/C(52,4) = 14950/270725 = 46/833 = appr .055

Math (Probability)
Prob(a one) = 1/6 prob(a one) twice = (1/6)(1/6) = (1/6)^2 .. prob(a one) ten times = (1/6)^10 = 1/60466176 = appr .000000016 These are independent events, that is, the die has no memory of what happened before, so each roll is a new event e.g. suppose we flip a coin 3 times. ...

Math - Calc/Algebra/Trig
your derivative is ok -4cos^2(x)sin(x)+sin(x) = 0 sinx( -4cos^2 x + 1 ) = 0 sinx = 0 ----> x = 0, ±?, ±2?, ... or 4cos^2 x = 1 cos^2 x = 1/4 cosx = ± 1/2 so x is in any of the 4 quadrants x = ±?/3, ±2?/3 , 4?/3, ±5?/3

math
"The sum of the 9th term is 117" makes no sense. Do you mean : the sum of the first 9 terms is 117 or The 9th term is 117 ?

You should have an idea what y = 1/x looks like, y = 1/(x+6) simply shifts the y = 1/x six units to the left. the 5 instead of the 1 means that the y value is 5 times as great, so it rises faster or there is a vertical stretch by a factor of 5 e.g. the point (1,1) on y = 1/x ...

Math
From your diagram, you should see than tan30° = 20/x, where x is the distance you need. However, a tower 20 cm high ???? You probably meant 20 metres.

Math
7. correct 8. area = 29 side = ?29 which is between 5 and 6 since 5^2 = 25 and 6^2= 36 , and your 29 falls between those two

Algebra
consecutive odd numbers are 2 apart let the first be x then the 2nd is x+2 and the third is x+4 "the sum of 4 times the largest is -191" makes no sense, "sum" is the result of addition , not multiplication If you meant that the result of 4 times the largest...

math
3/4x+5/6x=5x-125/3 the LCD is 12, so multiply each term by 12 9x + 10x = 60x - 500 easy from here.... 2(3x-7)+4(3x+2)=6(5x+9)+3 6x - 14 + 12x + 8 = 30x + 54 + 3 I am sure you an handle it from here

Math
For 1. , just replace the x with a+b 2. f(g(x)) = f(2x+5) = -2(2x+5)

Math
sum = -1/12 - 4/9 = -19/36 difference = -1/12 - (-4/9) = 13/36 (-19/36) ÷ (13/36 = -19/13

40 hrs a week at \$17.00 for 52 weeks = \$35,360 Where does the \$28,285.28 come from? No idea what the rest of the stuff is supposed to mean.

So much missing information! "WAGE---\$ 17.00-an hour---------ANUALLY---28,285.28" --- how many hours a week, how many working weeks in a year? "APARTMENT VALUE 17.34hrs/pay period towards an apartment value of \$934/month----ANUALLY---\$11,208----TOTAL-------\$39,...

algebra
6123/x = x + (1/2)x/x times x 6123 = x^2 + (1/2)x times 2 2x^2 + x - 12246 = 0 (x - 78)(2x + 157) = 0 x = 78 or x = -157 check: 6123/78 = 78 + remainder of 39 , which is 1/2 of 78 6123/-157 ? -157 + (????) the divisor is 78

Your first step should have been to simplify the expression: (x^2+x-6)/(x^2-9) = (x+3)(x-2)/( (x+3)(x-3) ) = (x-2)/(x-3), x ? 3 take over

IB Calculus
since a(t) = 2t - 16 when a(t) = 0 t = 8 v(8) = 64 - 16(8) + 4 = ......

Math
Find the volume of the large box Find the volume of the inner box Subtract the two results.

nope, look up distributive property in your text or notes and look up examples

Calculus
V = (4/3)?r^3 dV/dt = 4? r^2 dr/dt plug in the given stuff 50 = 4?(100)^2 dr/dt dr/dt = 50/(4?(100)^2 ) = .... cm/min

math
The first three are rational numbers. For the last one, no idea what the ## in 250## stands for

Math
original: Andy ---- a Jack ----- j after first give-away: Andy ---- a/2 Jack ----- j + a/2 after 2nd give-away: Jack --- (2/3)(j + a/2) Andy ---- a/2 + (1/3)(j+a/2) (2/3)(j + a/2) = 20 2(j + a/2) = 60 2j + a = 60 *** a/2 + (1/3)(j+a/2) = 20 times 6 3a + 2(j + a/2) = 120 3a + ...

math
The interest in the first year would simply be .1(14,000) = \$1,400 The fact of 5 equal payments for 5 years has nothing to do with this. Now for the 2nd year's interest, we need to do further calculations

statistics and probability
I agree with it, but I find I would like to meet that .8144 of a person.