Sunday
February 7, 2016

Posts by Reiny

Total # Posts: 32,835

Algebra/Math
done http://www.jiskha.com/display.cgi?id=1443624663
September 30, 2015

math
nope, think about what it means ... y^4 = yyyy y^3 = yyy so (y^4)(y^3) = (yyyy)(yyy) = y^7 when multiplying powers with the same base, keep the base and add the exponents
September 30, 2015

Equation find x xo tricky
I read that as: (x^x)√x = x(√x^x) square both sides x^(2x)(x) = x^2(x^x) x^(2x+1) = x^(x+2) 2x + 1 = x+2 x = 1
September 30, 2015

Math Answer Check
1. ok #2 why are you giving the negative result? cos 7π/2 = 0 so we need cos^-1 (0) = π/2 see: http://www.wolframalpha.com/input/?i=arccos%28cos%287pi%2F2%29%29+ #4. arctan (11/60) construct a right-angled triangle with opposite as 60 and adjacent as 11 r^2 = 11^2 + ...
September 30, 2015

Washington high
part at 10% --- x part at 7% = 12000 - x solve for x .1x + .07(12000-x) = 960
September 30, 2015

math
A = { 3, √2, 2√3, √9, √7} , but √9 = 3 which is rational, so you have 2 rationals out of the 5 well ?
September 30, 2015

correction - maths
(-5 i)(1/8 i) = (-5/8) i^2 , but i^2 = -1 = 5/8
September 30, 2015

Math
I will number your problems 1. ok 2. you need 6.5 ÷ 1/3 = 19.5 I would have expected a whole number, since it deals with people. So 19 would receive a full 1/3 of a box, and the 20th person would get less than 1/3 of a box 3. 3^2 = 9 , which is rational 1/5 is rational ...
September 30, 2015

math
don't you get a right-angled triangles with legs of 30 and 60 ? How about Pythagoras ?
September 30, 2015

math
tile : board = 1/3 ft : 1/2 yds = 4 inches : 18 inches = 2 : 9 area of tile : area of board = 2^2 : 9^2 = 4 : 81
September 30, 2015

TC Maths
recall that sinxcosx - sinycosy = cos(x+y) LS = (sin^2(x)-cos^2(y))/(Sinx cosx-Sinycosy) notice I inserted the absolutely necessary brackets to make the statement true = (sinx + cosy)(sinx - cosy)/(cos(x+y)) not getting anywhere ≠ tan(x+y) I usually test the equation ...
September 30, 2015

Word problem maths
Restating what Steve said in a slightly different way: sum of ages of all 21 boys = 21(14 3/12) = 299 1/4 sum of ages without oldest = 20(14 2/12) = 283 1/3 age of boy not included (oldest) = 299 1/4 - 283 1/3 = 15 11/12 which is exactly what Steve did
September 30, 2015

Calculus
well, let's set the velocity equal to zero ... 3t^2 - 12 = 0 3t^2 = 12 t^2 = 4 t = ± 2, but t ≥0 so the velocity is zero when t = 2 so what is the acceleration when t = 2 ??
September 29, 2015

Algebra I
Your text or notes should have definitions for a relation and a function In simple terms, a relation is any equation that contains two different variables, usually x's and y's e.g. x + y = 8 is a relation again, in simple terms, if I can isolate the y so it is ...
September 29, 2015

Calculus 1
well, there you go, how about that
September 29, 2015

Calculus 1
First of all -9/2x-5/2 is NOT an equation if you meant y = -(9/2)x - 5/2 then by golly, that is what my equation is 9x + 2y = -5 2y = -9x - 5 divide each term by 2 y = (-9/2)x - 5/2 My answer is correct.
September 29, 2015

Calculus 1
y^2=5x^4-x^2 2y dy/dx = 20x^3 - 2x dy/dx = (20x^3 - 2x)/(2y) = (10x^3 - x)/y at (-1,2) dy/dx = (-10+1)/2 = -9/2 so the tangent equation is 9x + 2y = c with (-1,2) lying on it, so -9 + 4 = c = -5 the tangent equation is 9x + 2y = -5 check: http://www.wolframalpha.com/input/?i=y...
September 29, 2015

Calculus 1
If it is an astroid, then it should be x^(2/3) +y^(2/3) =4 the way you typed it would result in a circle http://www.wolframalpha.com/input/?i=x%5E2%2F3+%2By%5E2%2F3+%3D4 (2/3)x^(-1/3) + (2/3)y^(-1/3) dy/dx = 0 x^(-1/3) + y^(-1/3) dy/dx = 0 dy/dx = -(x^(-1/3))/y^(-1/3) = -(x/y...
September 29, 2015

math
Question looks incomplete, but I think I can figure out what you want. Joel's speed --- x Kyle's speed --- x+10 6x + 6(x+10) = 780 solve for x and you got it
September 29, 2015

Indices
What is all this nonsense? Notice all 3 powers can be expressed as a power with base 2, thus as a power with base 4 P = (64)^-2 = (4^3)^-2 = 4^-6 Q = (1/16)^(1/3) = 16^(-1/3) = (4^2)^-1/3) = 4^(-2/3) R = 8√2 = 2^3(2^(1/2)) = 2^(7/2) = (4^(1/2))^(7/2) = 4^(7/4) the PQR...
September 29, 2015

algebra
first equation: 2x - 5y = 8 double the 2nd: 2x - 6y = -2 subtract them: y = 10 back into the original 2nd x - 3y = -1 x - 30 = -1 x = 29 x = 29, y = 10
September 28, 2015

Math
The hundred thousands digit is more than six XX7XX XX8XX XX9XX The thousands digit can be divided by the ones digit and since the number is even, the ones digit is even X47X2 X87X4 X48X2 X88X2 , but all digits are different, so skip the last, so X48X2 X49X2 X89X4 The ten ...
September 28, 2015

math
Place Shane in the first chair, then the remaining 5 students can be arranged in the 5 chairs in 5! or 120 ways
September 28, 2015

algebra
anything^0 = 1 , as long as you don't have 0^0
September 28, 2015

Math
base will be 8-2x by 6-2x height = x volume = x(8-2x)(6-2x) = 192 , where x<3 x(48 - 28x + 4x^2 = 192 4x^3 - 28x^2 + 48x - 192 = 0 x^3 - 7x^2 + 12x - 48 = 0 tried all the "nice" factors of 48, and found no solution. So I let Wolfram graph it and solve it to ge x...
September 28, 2015

math
see earlier post of the same question
September 28, 2015

math
increase in the length from 8 to 10 is 2cm percent increase = 2/8 = 25% old area = 40 new area = 70 increase = 30 percent increase = 30/40 = 75% did you realize that the increase will result in a distortion ? The percentage increase of the length is NOT the same as the ...
September 28, 2015

calculus
1. An amplitude of 1 applies to only the sine or cosine function. the given domain puts the angle in the 2nd quadrant. in that quad, the sine is positive and the cosine is negative, so it has to be y = cosx 2. I know that sin30° = sin(π/6) = 1/2 so csc (π/6) = 2 ...
September 28, 2015

precalc
there are 3 pairs of cofunctions sine vs cosine tangent vs cotangent secant vs cosecant Surely your text or notes have definitions of the reciprocal functions.
September 28, 2015

Math
Let's play "I spy" I spy with my little eyes two equal numbers sitting side by side.
September 28, 2015

math
Damon did this earlier today http://www.jiskha.com/display.cgi?id=1443455187
September 28, 2015

Math
In 5 hrs the first train went 5(68) or 340 km in the same 5 hrs, the 2nd train went 310 km So what do you think?
September 28, 2015

Math(ANSWERCHECK)!!
I got 7.159 but perhaps your skills of button-pushing are better than mine
September 28, 2015

MathHELP!
g(x) factors very nicely to g(x) = (x+1)^2 suppose you write it as g(x) = (x+1)^2 + 0 and you compare it to f(x) = a(x-h)^2 + k, which you must have learned and studied to do this topic
September 28, 2015

math
since there is a repeat of 117 in the decimal, it is rational. take 117/999 on your calculator your second answer of 32/100 is not in lowest terms as asked for 32/100 = 8/25
September 28, 2015

math
9. r = d/t multiply each side by t ---> d = rt 10. 3x - y = 10 add y to both sides 3x = y + 10 subtract 10 form both sides 3x - 10 = y strange way of doing equations: here is how I would do the last e.g. P = 2l + 2w P - 2l = 2W -----> I subtracted 2l from both sides P/2...
September 28, 2015

Math Help
What makes you think so ?
September 28, 2015

Kitondo boys
(2,2) ---> (-4,-4) (4,2) ---> (-8,-4) (3,4) ---> (-6,-8)
September 28, 2015

Help me! Geometry
the volume would be proportional to the cube of the linear measurements Since you doubled the 5 cm to 10 cm, the volume would be 2^3 or 8 times as large.
September 28, 2015

Math
really ?? you were given the hint. What does "sum" mean ?
September 28, 2015

Math
"If 3 is distributed from a number" What does that mean? Do you mean "subtracted from" ?
September 28, 2015

Math
girl's share --- x boy's share --- 3x 2(3x) + 3x = 144 etc
September 28, 2015

math
multi-choice --- x shorts - ----- 20-x x + 3(20-x) = 50 carry 0n
September 28, 2015

Math
hena --- x rina ---- 3x-100 Add them up and solve for x
September 28, 2015

Math
3/4 = .75 3/5 = .6 .75x - .6x = 9 .15x = 9 continue
September 28, 2015

Math
divide both sides by -1.4
September 28, 2015

Math
btw, your same question was posted by Marie about 5 years ago. I was able to read her post http://www.jiskha.com/display.cgi?id=1287543008
September 27, 2015

Math
Proofread your post, and retype in proper English
September 27, 2015

Math
Your post makes absolutely no sense to me. "a height of 12 feet per second " ???? are there two prisms ? Just guessing now: If one prism has a base area of 120 ft^2, and a height of 12 ft, then its volume is 1440 cubic feet if a second prism is 84 inches by 6 ft by ...
September 27, 2015

Math
Radius of large wheel --- R radius of smaller wheel -- r Circumf of large = 2πR circumf of small = 2πr 2πR - 2πr = 50 R - r = 25/π R = 25/π + r rotations of front wheel = 1440/(2πr) = 720/(πr) rotations of rear wheel = 2400/(2πR) = ...
September 27, 2015

math
looks good
September 27, 2015

Math
.8x = 256 x = 256/.8 you didn't post your choices but I bet x is one of them
September 27, 2015

physics
we have the vector: (35cos325°, 35sin325° x component = 35cos325 = appr 28.670 y component = 35sin 325 = appr -20.075 check: magnitude = √(28.67^2 + (-20.075)^2) = 35 tanØ = -20.075/28.67 = -.700209.. but Ø must be in VI, so Ø = 360-35 = 325
September 27, 2015

math
Suppose 3 apples cost 1 dollar how much would 54 apples cost? - would you know what to do? I am sure you would vs 3houses take 1 week to frame how long would it take to frame 54 houses ? To me they are the same type of question.
September 27, 2015

algebra
from the first: y = 9000-x , you had it backwards so .06x + .15(9000-x) = 1215 .06x + 1350 - .15x = 1215 -.09x = -135 x = 1500 then y = 9000-1500 = 7500 You also lost the equal sign in your last 2 lines
September 27, 2015

Math
I will assume you meant: 8log8(19) If that is the case, then the result is appr 11.328 none of your choices come even close to that. check your typing
September 27, 2015

Math
the LCD is (x+1)(x-1), so multiply each term by that x(x-1) - 2(x+1) = (x+1)(x-1) x^2 - x - 2x - 2 = x^2 - 1 -3x = 1 x = -1/3
September 27, 2015

Math
time at 10 mph --- x hrs time at 14 mph --- 5-x hrs since distance = rate x time 10x + 14(5-x) = 68 solve for x
September 27, 2015

Math
regular price ---- x (2/3)x = 360 x = ....
September 27, 2015

math
Now: Valeries age --- x Jose's age ------ 78-x 9 years ago: Val ----- x-9 Jo ------ 78-x-9 = 69-x at that time Jose was 3 times as old as Val 69-x = 3(x-9) solve for x
September 27, 2015

shammah int'l school
magnitude is the length of the hypotenuse of your right-angled triangle. the angle is Ø , such that tanØ = 35/30
September 27, 2015

Math
What are the choices?
September 27, 2015

Math
It would go 500!/21 times This is a very "large" number , it would be appr 500 digits long. Considering that 1 Billion has only 10 digits, you can imagine the enormity of this number.
September 27, 2015

Calculus
A lot of considering taking place here. plane A: direction of given first line = (2,1,4) so that becomes the normal to the plane and its equation must be 2x + y + 4z = C but it passes through (-1,0,2), so -2 + 0 + 8 = C = 6 PLane A: 2x + y + 4z = 6 Plane B: two directions are...
September 27, 2015

math
Now: Esm ---- x Greg ---- x+2 in 5 years: Esm = x+5 Greg = x+7 form your equation and solve
September 26, 2015

calculus
the way you typed the domain, which is your choice of x's you could use, is the set of real numbers for both expressions if you meant something like -9/(2+t^2) , since the denominator could never be zero is still the set of real numbers if the 2nd is 1 - 4/(2+t), clearly t...
September 26, 2015

math
area of rectangle including walk is 29 by 19 area = 551 area of pool = 25(15) = 375 so .....
September 26, 2015

Calculus
just do what it says ... f(x+h) , if h = .3 = f(x+.3) = 1/(x+.3) so (f(x+h)-f(x))/h = (1/(x+.3) - 1/x)/.3 = ((x - x - .3)/(x(x+.3))/.3 = ( -.3/(x(x-.3) )/.3 = -1/(x(x+.3))
September 26, 2015

Algebra
The way the question stands, it makes no sense. You would have to drain some of the solution and then add pure antifreeze. does it ask: How much of the current antifreeze, which is 20% , must be drained and the topped up with 100% antifreeze to have a 50% antifreeze ? Please ...
September 26, 2015

lgebra
your number do not add up to 963 you did not follow my pattern. x + x+1 + x+2 = 963 3x + 3 = 963 3x = 960 x = 320 so the three numbers are 320 , 321, and 322
September 26, 2015

lgebra
hint: if I told you that the first of 3 consecutive numbers is 17, wouldn't the next two be 18 and 19 ? what did I do to the 17 to get 18? what did I do to the 17 to get 20? if I told you that the first of 3 consecutive numbers is x , what would the next number be ??? let ...
September 26, 2015

ALGEBRA
width --- w length --- l = w + 4.15 use Ms Sue's formula
September 26, 2015

Proportions
Assuming the the burning of calories is in a direct proportion to the mass of the person doing the exercise, and since the time frame is the same, 130/194 = 250/x 130x = 48500 x = appr 373 cal's
September 26, 2015

differential calculus
I would write it as f(t) = 3t^(-1/2) f ' (t) = (-3/2)t^(-3/2) or = -3/(2t√t) just like the original function, the domain is t > 0
September 26, 2015

Math
Strange equation, I will assume you started with x^2 - 3x + 15.25 = 0 or x^2 - 3x + 61/4 = 0 or 4x^2 - 12x + 61 = 0 from: x^2 - 3x + 61/4 = 0 x^2 - 3x = -61/4 x^2 - 3x + 9/4 = -61/4 + 9/4 (x - 3/2)^2 = -13 x - 3/2 = ±√-13 x = 3/2 ± √-13 you had that, ...
September 26, 2015

Maths word problem need help
first day -- 1 = 2^0 2nd day -- 2 = 2^1 3rd day -- 4 = 2^2 .. 15th day ---- 2^14 or 16384 accumulate means you want the sum to be 1 million we have a geometric series with a = 1 r = 2 n = ?? sum(n) = 1000000 sum(n) = a(r^n - 1)/(r-1) 1000000 = 1(2^n - 1)/1 2^n = 1000001 take ...
September 26, 2015

Calculus
let the rate be r 4000(r)(4/52) = 50 r = 50(52)/((4000)(4)) = .165 or 16.5% There are actual companies dealing in paycheck-bridge loans that are charging $10 per week for a $200 quick "paycheck loan" that is a rate of ... 200(r)(1/52) = 10 r = 10(52)/200 = 2.6 or 260%
September 26, 2015

Arithmetic
let's add 15 hours to 8:00 am, that would put them coming in at 11:00 pm or at 23:00 using standard international units of time but with two sailors you can never tell.
September 26, 2015

Math
do you mean P( ...., -3/7) ? x^2 + (-3/7)^2 = 1^2 x^2 = 1 - 9/49 = 40/49 x = ±√40/7 = ± 2√10/7 we see that the y is negative, so the point could be in III or IV, thus the ±
September 26, 2015

algebra
let the daily rental fee be f let the mileage charge be m Jon: 9f + 300m = 315 3f + 100m = 105 Amanda: 5f + 240m = 186 jon x 5 -------> 15f + 500m = 525 Amanda x 3 ---> 15f + 720m = 558 subtract them: 220m = 33 m = 33/220 = 3/20 or .15 back into Jon 3f + 100(.15) = 105 f...
September 25, 2015

mathematics
given: (a^2 +b^2 +c^2) (x^2 +y^2 +z^2) = (ax +by +cz)^2 a^2x^2 + a^2y^2 + a^2z^2 + b^2x^2 + b^2y^2 + b^2z^2 + c^2x^2 + c^2y^2 + c^2z^2 = a^2x^2 + b^2y^2 + c^2z^2 + 2abxy + 2acxz + 2bcyz a^2y^2 + a^2z^2 + b^2x^2 + b^2z^2 + c^2x^2 + c^2y^2 = 2abxy + 2acxz + 2bcyz now if a:b:c = ...
September 25, 2015

math
using standard notation, you want cot(43° 41' 13") on my calculator, and most scientific calculators, there is a key labeled D°M'S and recall that cotØ = 1/tanØ so on mine the keystrokes are as follows 1 / tan 43 D°M'S 41 D°M'...
September 25, 2015

pre algebra HELP
I would write it like this (-12/3)(-8+(-4^2) -6)+2 = -4(-8 -16 -6) + 2 = -4(-30) + 2 = 120+2 = 122 the problem you had is the -4^2 you took it as (-4)^2 (-4)^2 = (-4)(-4) = 16 -4^2 = -1(4)(4) = -16
September 25, 2015

Math
area = 36 5/6 ft^2 = 221/6 ft^2 width= 5 2/3 ft = 17/3 ft length = area/width = (221/6) / (17/3) = (221/6)(3/17) = 13/2 or 6.5 ft you had that, so clearly it is not long enough to fit the 7 ft table Don't know why you would use 34/6 instead of the 17/3 Whether the table ...
September 25, 2015

interest
I will assume you have a typo and you meant 5.34% amount = 4720+ 4720(.0534)(9) = ....
September 25, 2015

Calculus
The rectangle is 2x by 3x with the semicircle on top of the 2x side Since there is a semicircle on top of the rectangle, the area = rectangle + semicircle = basexheight + (1/2)π x^2 = (2x)(3x) + π x^2/2 = 6x^2 + πx^2/2 perimeter = (1/2)(2πx) + 2x + 2(3x...
September 25, 2015

math
Poorly worded question, since there is no maximum value of y = x^4 - 8x http://www.wolframalpha.com/input/?i=plot+y+%3D+x%5E4+-+8x suppose we blindly proceed as usual ... dy/dx = 4x^3 - 8 = 0 for a max/min 4x^3 = 8 x^3 = 2 x = 2^(1/3) = appr 1.2599 subbing that in gives us y...
September 25, 2015

math
Intuitively, one should conclude that the sides would be equal, let's prove it let one side by x, then the other is √(144 - x^2) area = (1/2)x√(144-x^2) = (1/2)x(144-x^2)^(1/2) d(area)/dx = (1/2)[ x(1/2)(144-x^2)^(-1/2) (-2x) + (144-x^2)^(1/2) ] = 0 for a max ...
September 25, 2015

P6 maths
looks like I can't tell Mary and Amy apart.
September 25, 2015

P6 maths
mary's stamps --- m Amy's stamps ---- a .4m = .75a 40m = 75a m = 75a/40 = 15a/8 after giveaway Mary has .75m Amy has a + .25m a + .25m - .75m = 90 a - .5m = 90 2a - m = 180 2a - 15a/8 = 180 16a - 15a = 1440 a = 1440 m =2700 check my arithmetic
September 25, 2015

Calculus 1
Here is what your curve looks like http://www.wolframalpha.com/input/?i=plot+y+%3D+%7Cx%7C%2F%28sqrt%285-+x%5E2%29%29 notice that -√5 < x < √5 is our domain, with x = ±√5 as asymptotes Since (2,2) lies in quadrant I I will use y = x/√(5 - x...
September 25, 2015

Math
Numbers "dividing evenly" has nothing to do with the numbers being even. A number is said to divide into another evenly, if there is a zero remainder after the division. e.g. 15 ÷ 3 = 5 , (note none of the numbers are even) 15 is evenly divisible by 3 but 18 &...
September 24, 2015

Math
I assume you meant: (3/4) /8 + (1/3) /4 confirm please
September 24, 2015

Solving Linear Equations (Math)
width ---- x "The length of a rectangle is 5m shorter than three times the width" ---> length = 3x - 5 2x + 2(3x-5) = 46 should be easy to solve, go for it
September 24, 2015

Math
no 1+1 = 2 , which is not in the set of {0,1}
September 24, 2015

math for managers
What do you want done ? We are looking at the equation of a straight line
September 24, 2015

Math
amount at 5% --- x solve for x: .05x + .1(1800-x) = 165
September 24, 2015

math
prob(correct) = 1/5 prob(not correct) = 4/5 a) to have exactly 5 correct = C(12,5) (1/5)^5 (4/5)^7 = appr .05315 b) prob(2 correct) = C(12,2) (1/5)^2 (4/5)^10 = ... c) 4 or fewer correct ---> 0 correct + 1 correct + 2 correct + 3 correct + 4 correct d) to get 75% he needs ...
September 24, 2015

Calculus
What method are you using to solve a cubic, since there is no simple "formula" method ? your two answers do not satisfy the equation here is what Wolfram has http://www.wolframalpha.com/input/?i=solve+x%5E3-3x%2B3%3D0 click on "approximate forms" to see one...
September 24, 2015

Algebra 2
no you were correct at 8/√2 * √2/√2 = 8√2/(√2)^2 , but √2^2 is equal to 2 = 8√2/2 = 4√2 If you have any others, why not check your answer using a calculator e.g. 8/√2 = 5.6568... 4√2 = 5.6568... my answer is correct
September 24, 2015

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