Monday
May 2, 2016

Posts by Reiny

Total # Posts: 34,416

math
(x,y) ---> (x-2, y-1) then (x-2,y-1) --> (x-2 + 5, y-1 + 6) or (x,y) ---> (x+3, y+5) illustrate by picking any point and seeing what happens.
February 10, 2016

Math
solve for x .28 x = 168 x = 168/.28 = ...
February 10, 2016

math
x - 5 ≤ 20 "at most" means it can't go over 20, so it has to be less than. Your expression said > 20 Furthermore, by saying the difference between a number and 5, you don't say which way we are subtracting. e.g. if I say what is the difference ...
February 10, 2016

math
Just did it when you were Tommy http://www.jiskha.com/display.cgi?id=1455143548
February 10, 2016

i need help please math
reflection in the y-axis (x,y) ---> (-x,y) reflection in the x-axis (-x,y) ---> (-x, -y) so (x,y) --> (-x,-y) , which is a reflection in the origin. pick a point and illustrate it on a grid. e.g. watch what happens to (3,5)
February 10, 2016

Math PLEASE HELP
Just add them up, then divide by 10. That would be just like finding the average. Hint: change them to decimals, they all come out nice that way, simpler to add them that way e.g. 4 ¼ kg = 4.25 kg
February 10, 2016

Mathematics
look at my attempt here http://www.jiskha.com/display.cgi?id=1455132924
February 10, 2016

Cal 2
V = π ∫(9/x^2) dx from x=3 to 5 = π( -9/x) | 3 to 5 = π(-9/5 - (-9/3) ) = π(6/5) = 1.2π cubic units
February 10, 2016

Algebra
Well, you got it 4t^2 - 20t - 150 = 0 by the formula t = (20 ± √2800)/8 =9.11 or a non-admissible negative value
February 10, 2016

Maths
x^2+2xy+2y^2+6y = x^2+2xy+y^2 + y^2+6y = (x+y)^2 + y(y+6) = S x _ y _ S 0 0 0 1 0 1 2 0 4 3 0 9 4 0 16 ... 0 1 8 0 2 20 .. -------no future here, S gets bigger try negative values 0 -6 36 1 -6 25 .. 5 -6 1 5 -5 -5 1 -1 -5 2 -2 -8 3 -3 -9 <-------- LOOKS LIKE THAT IS IT 4 -4...
February 10, 2016

Geometry
I assume that you have listed the two triangles in matching vertices, that is, A <--> D , etc let AB = 2x then DE = 3x , must be in the ratio of 2:3 if AB = 2BC 2x = 2BC BC = x given: DE = 3BC DE = 3x , (we already knew that) then EF = 6x
February 10, 2016

Math
I will assume you mean m^9t^-10/(m^-4t^-5) = m^13 t^-5 or m^13/t^5 you are correct
February 10, 2016

Cal 2
no need for calculus. your solid is a fulcrum formed by the following: You have a cone on its side, (the x-axis is the axis of the cone) height = 3, radius = 9 the other : height = 5, radius = 15 V = (1/3)π(15^2)(5) - (1/3)π(9^2)(3) = (1/3)π (1125 - 243) = 882&#...
February 10, 2016

math
$1,4000 ?? I assume you meant $1,400 what is .65(1400) ?
February 10, 2016

algebra
complex roots always come in conjugate pairs, so we have x = -3i and x = 3i two factors are (x + 3i) and (x- 3i) (x+3i)(x-3i) = x^2 - 9i^2 = x^2 + 9 Using long algebraic division, you should get ( 3x^4+5x^3+25x^2+45x-18) ÷ (x^2+9) = 3x^2 + 5x + 2 the quadratic formula ...
February 10, 2016

math
Using the basic definitions: a + 4d = -12 a + 9d = 27 subtract them 5d = 39 d = 39/5 or 7.8 sub back in .... a+4(7.8) = -12 a = -43.2 sequence is: -43.2 , -35.4, -27.6, -19.8, -12, ... term15 = a + 14 d = ..... B) The first three terms of an A. P are x and the 10th term. That ...
February 10, 2016

Math
My crystal ball does not seem to be working today. I just can't seem to conjure up your parallelogram.
February 10, 2016

Cal 2
Just did this http://www.jiskha.com/display.cgi?id=1455128294
February 10, 2016

Cal 2
no Calculus needed. extend the sides to form the original cone. let the height of the added cone be h by ratios h/13 = (h+25)/30 30h = 13h + 325 17h = 325 h = 325/17 volume of fulcrum = (1/3)π(30^2)(25 + 325/17) - (1/3)π(13^2)(325/17) = (1/3)π[900(25+325/17) - ...
February 10, 2016

math
basic trig: sinØ = 5/8 = .. Ø = appr 38.7°
February 10, 2016

Algebra 2
from the first: y = -2x-11 into the 2nd 3x - 4(-2x-11) = 11 3x + 8x + 44 = 11 11x = -33 x = -3 No need to find y, the only one with x=-3 is the third one. To make sure, sub (-3,-5) into both equations.
February 10, 2016

Math
solve: 15m = 5m + 1100
February 10, 2016

maths class8
see your previous post
February 10, 2016

maths
now: son --- x father -- 5x 5 years ago: son = x-5 father = 5x-5 5x-5 = 7(x-5) solve for x
February 10, 2016

algebra
I started with x = ±1 and got x= 1 so (x-1) is a factor and also found x = ±2 to work so (x+2)(x-2) were factors so x^4+6x^3-11x^2-24x+28 = (x-1)(x-2)(x+2)(x .... ?) so far my constant multiply to get 4, but I need +28, so the last digit must be +7 x^4+6x^3-11x^2...
February 10, 2016

let's try again - Math
oops, just noticed my third equation is wrong Here we go again: I will use the notation a = (2,-1,1) , b= (1,-3,1) , c=(-2,1,-3) and d=(3,2,5) so 2p + q - 2r = 3 -p - 3q + r = 2 p + q - 3r = 5 add the 2nd and 3rd: -2q - 2r = 7 2q +2r = -7 ** double the 2nd , then add to the ...
February 10, 2016

Math
I will use the notation a = (2,-1,1) , b= (1,-3,1) , c=(-2,1,-3) and d=(3,2,5) so 2p + q - 2r = 3 -p - 3q + r = 2 -2p + q - 3r = 5 add 1st and 3rd: 2q - 5r = 8 ** double the 2nd , then add to the first: -5q = 7 q = -7/5 into ** -14/5 - 5r = 8 -5r = 54/5 r = -54/25 into the 1st...
February 10, 2016

Math
number of P5's --- x number of P1's --- y x+y = 16 5x + 1y = 44 subtract them: 4x = 28 x = 7 y = 9 check: 5(7) + 1(9) = 44
February 10, 2016

math
Case1: the number of hours is single digit hours --- h unit digit of minutes --x tens digit of minutes --y x+10y = 5h ** x+y+h = 15 h = 15-x-y 5h = 75 - 5x-5y *** equating ** and *** x+10y = 75-5x-5y 6x + 15y = 75 2x + 5y = 25 x = (25-5y)/2 --> 25 - 5y must be even so it ...
February 10, 2016

Trigonometry
Once you make your diagram, it is easy to see that we can use the cosine law. AC^2 = 560^2 + 320^2 - 2(320)(560)cos104° = 502704.8074 AC = appr 709 miles
February 10, 2016

algebra
f(g(-7)) = f(-14-6) = f(-20) = 60-4 = 56
February 9, 2016

Mathh
5 marbles out of 12 Prob(red) = 5/12
February 9, 2016

math
yes, but usually a unit of 1 is used 2.5 inches : 79 miles 1 inch : 79/2.5 mile 1 inch : 31.6 miles If you use the same units, they can be skipped in the scale ... 31.6 miles = (31.6)(12)(5280) inches 2002176 inches so you could state the scale as 1 : 2,002,176
February 9, 2016

mathemathics
Just did this in your earlier post of this.
February 9, 2016

math
let the unit digit be x then the hundred digit is 2x let the tens digit by y so the number is 100(2x) + 10y + x = 201x + 10y the number reversed is 100(x) + 10y + 2x = 102x + 10y 201x+10y - (102x+10y) = 396 99x = 396 x = 4 looks like y can be any digit from 0 to 9 the original...
February 9, 2016

MATH
let the angles be 3x and 2x their sum = 90° 5x = 90 x = 18 the smaller angles is 2x = 36°
February 9, 2016

Math
I attempted this question yesterday. Had some doubts about the typing http://www.jiskha.com/display.cgi?id=1454969855
February 9, 2016

shelby
rise --- x m hypotenuse -- x+32 run --- x+31 x^2 + (x+31)^2 = (x+32)^2 x^2 + x^2 + 62x + 961 = x^2 + 64x + 1024 x^2 - 2x - 63 = 0 (x-9)(x+7) = 0 x = 9, or x = -7 which would be silly the sides are 9, 40, and 41 check: 9^2 + 40^2 = 41^2, true!
February 9, 2016

algebra
L = k(1/d^2) for the given: 75 = k(1/225) k = 16875 L = 16875/d^2 then if d = 47 L = 16875/47^2 = 7.6 decibels
February 9, 2016

college algebra
b) .12x c).15y d) your equation should say .12x + .15y = 64500 times 100 12x + 15y = 6450000 divide it by 3 4x + 5y = 2150000 first equation times 4 4x + 4y = 2000000 subtract them: y = 150,000 then x = 350,000 check: .12(350000) + .15(150000) = 64500
February 9, 2016

algebra
"Type your answer in the box provided "... tells me that you simply want us to do your assignment for you. This question is of such fundamental nature, that you absolutely MUST know how to do it. What are your steps so far ?
February 9, 2016

Cal 2
the x-intercepts for both functions are c and -c If you look at your sketch there is symmetry about the y-axis as well, so we could just take our area from 0 to c 4∫(c^2 - x^2) dx = 230 from 0 to c ∫(c^2 - x^2) dx = [c^2 x- (1/3)x^3] from 0 to c = (c^3 - (1/3)c^3...
February 9, 2016

algebra
the simplest right-angled triangle has sides 3,4, and 5 If you did not know that, let the three sides be x, x+1, and x+2 x^2 + (x+1)^2 = (x+2)^2 x^2 + x^2 + 2x + 1 = x^2 + 4x + 4 x^2 - 2x - 3 = 0 (x-3)(x+1) = 0 x = 3 or x = -1, the last one is silly x=3 conclusion ....
February 9, 2016

Math- Calc
done, look back a few posts
February 9, 2016

Algebra
(6x^-2)^2(0.5x)^4 = (36x^-4)(1/16)(x^4) = 36/16 x^0 , but x^0 = 1 = 36/16 = 9/4
February 9, 2016

Algebra
at the x-intercepts, y = 0 , so ... x^2 + 0 + 8x - 0 - 49=0 using completing the square: x^2 + 8x +16 = 49+16 (x+4)^2 = 65 x+4 = ±√65 x = -4 ± √65 or appr 4.06 or appr -12.06 confirmation. Notice your equation represents a circle http://www....
February 9, 2016

Math
f(x) = |(x+9)(x-7)| the function y = (x+9)(x-7) would have x-intercepts at -9 and 7 , and it would dip below the x-axis between these two values. So the |...| flips that part above the x-axis, causing CUSPS at x =-9 and x=7 the derivative does not exist for those two values.
February 9, 2016

Maths
I will assume you meant to say: The first term of an arithmetic sequence is 23 and the 12th term is 72. So a = 23 , and a+11d = 72 23+11d = 72 11d = 49 d = 49/11 take over, all you have to do is use the formulas
February 9, 2016

algebra equations
Bosnian, you are correct if the number is 31/6 then 31/6 + 5(31/6) - 4 = 31/6 + 155/6 - 4 = 31-4 = 27
February 9, 2016

Math
if you want the prob of a 5 OR a 6 OR an odd, then it would be 4/6 = 2/3 If you want the prob of a 5 AND a 6 AND an odd, then it would be 0
February 9, 2016

Math
Not clear if the new monies are transferred from the other person's wallet, or if they are new monies. e.g. Do the 80 cents that Cheryl puts in her wallet come from Sally? Please clarify.
February 9, 2016

math
number of plates = 10x10x10 x 26x26 = 676,000
February 9, 2016

Math
just add them 4y = 28 y = 7 sub back into the 2nd x - y = 15 x - 7 = 15 x = 22
February 8, 2016

optional math
for AP first -- a fourth --a+3d ninth -- a+8d these are to be in GP (a+3d)^2 = a(a+8d) a^2 + 6ad + 9d^2 = a^2 + 8ad 9d^2 - 2ad = 0 d(9d -2a) = 0 d = 0 or a = 9d/2 reject d=0, because the sequence simply becomes a, a, a, .... which technically is an AP as well as a GP if a = 9d...
February 8, 2016

Math
From the many ways your ambiguous way of typing could be interpreted , I will choose (16x-12)/(4x^2+5x-6) - 3/(x+2) = 4(x-3)/( (x+2)(4x-3) ) - 3/(x+2) = (4(x-3) - 3(4x-3))/((x+2)(4x-3)) = (4x - 12 - 12x + 9)/((x+2)(4x-3)) = (-8x - 3)/((x+2)(4x-3))
February 8, 2016

Maths
make a sketch to see that the 10.5 cm becomes the hypotenuse of the cone and the circumference of the cone is the arc length of the sector. 160° = 160/180π radians = 2.7925.. radians arc = 2.7925(10.5) = 29.32153.. this becomes the circumf of the base of the cone 2&#...
February 8, 2016

Algebra
time = distance/rate 90 miles/hour = 90(5280) ft / 3600 seconds = 132 ft/s so time = 60.5 ft/132 ft/s = .45833... seconds = appr .46 seconds
February 8, 2016

Geometry
your value of a is correct. Actually your given triangle is a 30-60-90 right-angled triangle with sides in the ratio 1 : √3 : 2 = 50: 50√3:100 You didn't say which of the legs is the x and the other the y. Assume the x is opposite the 30° angle then the ...
February 8, 2016

pre-calculus
your x(x-3)<2 or x(x-3)<2 are the same expression did you mean: x(x-3)<2 or x(3-x)<2 ? some preliminary... clearly any negative value of x will work, since -(+) is negative which is < 2 notice that is true for all x < 1 so x < 1 also if x = 2, we have 2|-1...
February 8, 2016

math
(3^x)(5^x) + 1 = 20 (15)^x = 19 use logs x log15 = log 19 x = log19/log15 = appr 1.08729 Use your calculator to check, it works
February 8, 2016

Math
areas of similar shapes are proportional to the square of their corresponding sides ratio of their areas is 2^2 : 3^2 = 4 : 9
February 8, 2016

basic algebra
unit digit --- x tens digit ----x+4 x^2 + (x+4)^2 = 26^2 solve the quadratic
February 8, 2016

basic algebra
marko's rate --- 1/x carlo's rate --- 1/y clyde's rate --- 1/z combined rate of all three = (xy + xz + yz)/(xyz) xyz/(xy + xz + yz) = 6 xyz = 6((xy + xz + yz) ** Carlo and Marko 1/(1/x + 1/y) = 8 xy/(x+y) = 8 xy = 8(x+y) *** clyde and marko 1/(1/x + 1/z) = 9 xz = 9...
February 8, 2016

math
projection of <-5,3) onto <1,4> = (-5+12)/√(1^2+4^2) = 7/√17 or 7√17/17
February 8, 2016

Pre-cal
short cut 4cis (7pi/6)*3cis(pi/3) = 12 cis(7π/6+π/3) , by De Moivre's theorem = 12cis(3π/2) but you wanted it in rectangular form = 12(cos 3π/2 + i sin 3π/2) = 12(0 - 1 i) = -12i long way (if you don't know the above law): 4cis (7pi/6) = 4(cos ...
February 8, 2016

MATH PLZ HELP!!!!
no area = (1/2)(height)(sum of parallel sides) = (1/2)(8)(22.5+9.5) = 128
February 8, 2016

basic algebra
tens digit --- x units digit -- x+6 the value of the number is 10x + x+6 = 11x + 6 11x = 2(x + x+6) + 8 11x = 4x + 14 7x=14 x=2 the number is 28
February 8, 2016

Math
1.-2v-7=-23 ---> correct A.)15 B.)8*** C.)-8 D.)-15 4.-2(m-30)=-6m ----> no A.)-15 B.)-13 C.)-8*** D.)8 -2m + 60 = -6m 4m = -60 m = -15 5.3n+2=8+2n ----- no A.)3 B.)4*** C.)5 D.)6 <----- 6.Simplify the expression. -----no -6-7(c+10) A.)64-7c B.)-76-7c C.)4-13c D.)-16-...
February 8, 2016

math
how about solving the proportion t/279 = 6/372
February 8, 2016

basic algebra
let the width of the cardboard be x then it's length is 17-x 2 inches cut off each dimensions leaves the base of the box to be x-4 and 17-x-4 x-4 and 13-x (x-4)^2 + (13-x)^2 = 49 x^2 - 8x + 16 + 169 - 26x + x^2 = 49 2x^2 - 34x + 136 = 0 x^2 - 17x + 68 = 0 x = (17 ±...
February 8, 2016

basic algebra
old fraction: (x-4)/x new fraction: 2(x-4)/(x-2) and then it said: (x-4)/x + 2(x-4)/(x-2) = 3 multiply each term by x(x-2) (x-4)(x-2) + 2(x)(x-4) = 3x(x-2) x^2 - 6x + 8 + 2x^2 - 8x = 3x^2 - 6x -8x = -8 x = 1 the fraction was -3/1 ??? new fraction = -6/-1 = 6 The original ...
February 8, 2016

math
well, how many numbers on a cube are less than 6 ??
February 8, 2016

Probability
If we add two evens, we get an even If we add two odds, we get an even If we add an even and an odd, we get an odd Let's look at this simplified scenario, of 4 numbers +1 . 2 .3 .4 1: 2 3 4 5 2: 3 4 5 6 3: 4 5 6 7 4: 5 6 7 8 clearly half the sum's are even, half are ...
February 8, 2016

basic algebra
smallest angle --- x middle sized -----y largest ---------x+y x + y + x+y = 180 x+y = 90 *** x-y = (2/3)(x+y) 3x - 3y = 2x + 2y x = 5y sub into *** 5y + y = 90 y = 15 x = 75 smallest = 15 middle sized = 75 largest = 90
February 8, 2016

math
number of boys --- 3x number of girls ---- 7x total campers = 10x after leaving: total campers = 10x-87 number of boys = 3x/2 number of girls = (8/10)(7x) = 28x/5 3x/2 + 28x/5 = 10x - 87 times 10 15x + 56x = 100x - 870 -29x = -870 x = 30 number of girls at start = 7x = 210 ...
February 8, 2016

math
using elimination: first one times two: 6x + 4y = -36 2nd one times three: -6x + 15y = -78 add them ... 19y = -114 y = -6 sub back into the original first ..... take over
February 8, 2016

Math
deductions = 12% + 17% + 3% = 32% leaving him with 68% of his salary what is .68(26965) ?
February 7, 2016

Business
PV = 3000(1.04)^-1 + 3000(1.04)^-2 = ...
February 7, 2016

math
Why use all those variables? let the weight of the command module be x now just translate the given English into Math "the service module weighed 3000 lbs less than 5 times the weight of the command module" ---> sm = 5x-3000 "The lunar module weighed 1000 lbs...
February 7, 2016

math
My goodness! All those words for such a simple problem. And you posted it about 4 times. Florist: Income per click = 1125/500 = $2.25 per click income = 2.25c , where c is then number of clicks Pizza place: income per click = 200/100 = $2.00 per click income = 2c , where c is ...
February 7, 2016

Pre Algebra
amount into CD --- x amount into Ed Account --- 2x+7000 x + 2x+7000 = 52000 all yours ...
February 7, 2016

math
nP5 = n!/(n-5)! your equation: n!/(n-5)! = 14n!/(n-4)! n!/(n-5)! = 14n!/(n-4)(n-5)! 1 = 14/(n-4) n-4 = 14 n = 18 check: my calculator says P(18,5) = 1028160 and P(18,4) = 73440 and 14(73440) = 1028160
February 7, 2016

math 2
centre is the midpoint of the diameter, so (4,0) equation: (x-4)^2 + y^2 = r^2 plug in (5,1) to find r^2 all done!
February 7, 2016

maths
For your AP term4 = a+3d = 6 ** term11=a+10d = 34 *** subtract them 7d = 28 d = 4 sub in ** a+12 = 6 a = -6 the AP is -6, -2, 2, 6, 10, ...
February 7, 2016

pre-calclus
I have a feeling that you have a typo and this is supposed to be either a sine or cosine function Assuming I am correct ..... for any sine function in the form: y = a sin (k(Ø + d)) + c |a| is the amplitude the period is 2π/k the phase shift is d units to the left...
February 7, 2016

Precalc
just use a simple ratio newtax/85000 = 1500/64000
February 7, 2016

radicals
Is that √8( √(9ab)/√(3b) + √(27a) ) or √8 { √(9ab)/ [√(3b) + √(27a) ] } furthermore, is it (√9)(ab) or √(9ab) ? same for the other square roots .
February 7, 2016

math
400(1+i)^2 = 480 (1+i)^2 = 1.2 1+i = 1.095445 i = .095445 new rate = .095445 + .02 = .115445 new amount = 400(1.115445)^2 = 497.69
February 7, 2016

Math
assuming that at t = 0 the height was zero (at ground level) Let's use a sine curve. The amplitude is 34 and the period is 2.5 seconds 2.5 = 2π/k k = π/1.25 so our basic curve is h = 34sin(πt/1.25) We need to raise this 34 cm so it doesn't go below road ...
February 7, 2016

Math
I answered the first question back in 2012 http://www.jiskha.com/display.cgi?id=1326819217 See if you can follow the same way for the 2nd question. The second question is actually easier Be sure to use 60 seconds for 1 minute at the end
February 7, 2016

Math
In any cyclic quad, the opposite angles are supplementary, that is, they add up to 180°
February 7, 2016

Is444
number of dimes --- x number of quarters -- x+10 number of nickels = 2(x+10) now for the "value": 10x + 25(x+10) + 5(2(x+10)) = 530 solve for x, then plug into my definitions.
February 6, 2016

algebra
dimes --- d nickels -- n equation dealing with number of coins: n+d = 28 n = 28-d equation dealing with the value of your coins: 10d + 5n = 195 divide by 5 2d + n = 39 sub in the other equation: 2d + 28-d = 39 d = 11 n = 28-11 = 17 She has 11 dimes and 17 nickels check: total...
February 6, 2016

Math
remember , two of the sides would be equal let the base be x let each of the equal sides by y x + 2y = 36 or x = 36-2y *** 5x + 2 = 3y 5x - 3y = -2 sub *** into this last equation 5(36-2y) - 3y = -2 180 - 10y - 3y = -2 -13y = -182 y = 14 then x = 36-28 = 8 the base is 8 and ...
February 6, 2016

Calculus with Analytical Geometry
Sorry, I was using the "Amount" formula should have been: PV = 3500( 1 - 1.06^-3)/.06 = 9355.54
February 6, 2016

Calculus with Analytical Geometry
PV = 3500( 1.06^3 - 1)/.06 = ...
February 6, 2016

@sam - math
Sam, it would have been nice if you had given bobpursley credit for his solution that you just cut-and-pasted. http://www.jiskha.com/display.cgi?id=1402557272
February 6, 2016

math
Assuming you know the relationship between distance, velocity and acceleration, v = at , no constant since at t=0 , v=0 d = (1/2)at^2 , no constant since at t=0, d = 0 but when t = 10, d = 500 (1/2)a(100) = 500 a = 10 acceleration is 10 m/s^2,
February 6, 2016

math
no, since the 6% is compounded quarterly you must divide .06 by 4 i = .06/4 = .015 so 350(1.015)^32 in the next one you would have to divide .06 by 12 to get i = .005 using the annuity formula 150( 1.005^n - 1)/.005 = 8000 (1.005^n -1)/.005 = 53.3333... 1.005^n - 1 = .26666...
February 5, 2016

Math, Help me check my answers
the last two are correct for the first one, complementary angles add up to 90°, so it is angle 4 and angle 5 You picked opposite angles.
February 5, 2016

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