Monday
November 24, 2014

Posts by Reiny


Total # Posts: 27,933

Algebra, help please!!!
for each one, multiply each term by the LCM e.g. c: 5/6 - 2/3 x = 3/4 LCM = 12 so multiply each term by 12 (5/6)(12) - (2x/3)(12) = (3/4)(12) 10 - 8x = 9 -8x = -1 x = 1/8 do the others the same way in b) I would cross-multply first to get (1/3)x = 3/4 , the proceed by ...
October 11, 2014

another math equation
a statement such as a/4 = b/5 = 2/3 means that all fractions equal each other and are equal to 2/3 so set each one equal to 2/3 a/4 = 2/3 or a = 8/3 b/5 = 2/3 or b = 10/3 the ab = (8/3)(10/3) = 80/9 or 8 8/9
October 11, 2014

another math equation
if you mean a/4 = b/5 = 2/3, then do it the same way I just showed you for your previous post
October 11, 2014

math equation
type your fractions this way: a/4 = b/5 = 3 then: a/4 = 3 ---> a = 12 and b/5 = 3 --> b = 15 finally: a+b = 12+15 = 27
October 11, 2014

Math
are you not familar with the basic fundamental rules of solving equations. I "moved" the +7x from the left side of the equation to the right side of the equation or 7x - 6y -7x = -7x + 42 -6y = -7x + 42 now divide every term by -6 etc
October 8, 2014

Math
quick way: If the line is expressed in the form Ax + By + C = 0 the slope is -A/B , note the value of C does not enter the picture. so for 7x - 6y = 42 the slope is -7/(-6) = 7/6 or , by the usual grade 9 way 7x - 6y = 42 -6y = -7x + 42 y = -7x/-6 + 42/-6 y = (7/6)x - 7 ,,,, ...
October 8, 2014

Calculus
let the side parallel to the canyon wall be y ft let each of the other two shorter and equal sides be x 2x + y = 500 y = 500-2x area = xy = x(500-2x) = 500x - 2x^2 since you labeled it Calculus d(area)/dx = 500 - 4x = 0 for a max of area 4x = 500 x = 125 when x = 125 , y = 500...
October 8, 2014

ap calc
2x - ( x^2 + 4)/x = 0 times x 2x^2 -(x^2 + 4) = 0 x^2 = 4 x = ± 2 if x = 2, y^2 = 4, and dy/dx = 0 , of course ! a horizontal line through (2,4) is y = 4 if x = -2 ....... (you do it) verification of result at http://www.wolframalpha.com/input/?i=plot+y%5E2+%3D+%28x%5E2...
October 8, 2014

algebra
See my reply to your previous post of this problem check your typing.
October 8, 2014

Sara - math help
Please don't attach a new question to the replies of a new question, post it as a new question. While you are replying to my first concern, here is your second problem: you claim that you have a linear system of equations, but xy = 7 is not linear, it would be a curve. ...
October 8, 2014

math help
what does x 10 mean? did you mean 10x or x^10 or .... I can't see where you get f(7) = -10
October 8, 2014

algebra
I would guess at y = (x-1)(x + 2)(x + 2)(x + 3) or y = 17(x-1)(x+3)(x+2)^2 It asked for one such function expand it if you feel you must. ( placing a constant in front does not change the x-intercepts )
October 8, 2014

analytic geometry
ummh, doesn't it say the y is the opposite of the x ? (and the x is the opposite of the y ?) so (7,-1) ----> (1, -7) check: plot the points and see how they relate to the line y = -x
October 8, 2014

math
if width is 1/2 the length, then length is twice the width, so width --- x length ---2x 2(x) + 2(2x) = 90 there is your equation, the x would be the width as I defined it as such.
October 8, 2014

math (need check answer)
for #1, I am sure you meant 3x + 4y #2 is correct
October 8, 2014

Math
since in both cases have a monomial as its denominator, all we have to do is mutiply by i/i I will do the first, you do the second (2+4i)/i = (2+4i)/i * i/i = (2i + 4i^2)/i^2 = (2i - 4)/-1 = 4 - 2i (remember i^2 = -1)
October 8, 2014

Algebra
I don't understand your solution. What do you mean "the graph only goes up to 10" ? There are an infinite number of points , all will lie in the same straight line change the equation to y = -5x - 4 now pick any x you feel like, and evaluate the corresponding y e...
October 8, 2014

algebra
coming down rate --- x mph going up rate -----< x-3.5 time going up = hill/(x - 3.5) hill/(x - 3.5) = 4 hill = 4(x - 3.5) time going down = hill/x hill/x = 135/60 = 9/4 hill = (9/4)x 4(x - 3.5) = (9/4)x 16(x-3.5) = 9x 16x - 56 = 9x 7x = 56 x = 8 rate going down is 8 mph (...
October 8, 2014

math
Very straight-forward There are 2 red tens, the 10 of hearts, and the 10 of diamonds so prob(red ten) = 2/52 = 1/26 Your last sentence makes no sense to me.
October 8, 2014

Algebra
Looks like your question with one number changed. Just follow the solution http://www.jiskha.com/display.cgi?id=1412722973
October 7, 2014

Algebra
And the question is .... ?
October 7, 2014

Math
http://www.jiskha.com/display.cgi?id=1412721979
October 7, 2014

Algebra
first day, number of freebies = 6742/175 = appr 38.5 which means the 39th free person has not yet arrived so 38 free passes 2nd day, number of freebies = 5487/175 = appr 31.3 so 31 free passe total = 38+31 = 69
October 7, 2014

calculus
Yup, Steve is right, I had the plane flying away from the kangaroo, should have read it more carefully. The numerical answer would simply change to a positive rate of change of the angle.
October 7, 2014

calculus
Did you try to find an error in my solution? How do you know it is wrong?
October 7, 2014

calculus
Why are you posting this again ? I answered your same question about 3 hours ago. Always check back on your posts, mark their time, and they are easy to find that way. http://www.jiskha.com/display.cgi?id=1412721979
October 7, 2014

algebra 2
This is not that hard x≥ 0 , everthing to the right of the y-axis y≥ 0 , everthing above the x-axis So far you are in quadrant I of the x-y plane y ≤ 3 , everthing from the above, but also below the horizontal line y = 3 lastly y ≤ -x + 5 sketch a line ...
October 7, 2014

7th grade math
Ross --- x Larue --- 3x - 10 3x-10 = 11 3x = 21 x =7 Ross scored 7 and Larue scored 11
October 7, 2014

Math
1. equation will be y = 2(x-3)^2 - 4 since the parabola opens upwards, there will be a minimum That minimum is -4 and it occurs when x = 3 2. same equation if your equation is y = a(x-p)^2 + q the vertex is (p,q) it will open up if a>0 it will open down if a< 0 the axis ...
October 7, 2014

Math
1. if GS , then k^2/2 = 8/k^2 k^4 = 16 k^2 = ± 4 but k^2 can't be -4 k^2 = 4 k = ± 2 2. looks like a = 2 , r = 3 find term(8) Just use your basic formula
October 7, 2014

Math
common ratio = r = 6/2 = 3 (I took the easiest fraction) first term = a = 2/9 term7 = ar^6 = (2/9)(3^6) = 162 2. ar^2 = 2 ar^4 = 1/2 divide the 2nd equation by the first r^2 = 1/4 r = ± 1/2 then in ar^2 = 2 a(1/4) = 2 a = 8 3. a) x/(1/2) = (1/3)/x x^2 = 1/6 x = ±...
October 7, 2014

Math
it will depend on what happened in the first draw. case1 , first is green, 2nd is green prob = (8/12)(7/11) = 14/33 case2 , first is not green, 2nd is green prob = (4/12)(8/11) = 8/33 prob(of your event) = 14/33 + 8/33 = 22/33 = 2/3
October 7, 2014

MATH
speed of boat --- x mph speed of current -- y mph 16/(x+y) = 2 2x + 2y = 16 x + y = 8 28/(x-y) = 7 7x - 7y = 28 x-y = 4 add them: 2x = 12 x = 6 then mentally y = 2 the speed of the boat is 6 mph, and the current is 2 mph
October 7, 2014

Math radical equations
1. √(m-1) + 5 = m-2 √(m-1) = m - 7 square both sides m-1 = m^2 - 14m + 49 m^2 - 15m + 50 = 0 (m-5)(m-10) = 0 m = 5 or m = 10 BUT, since we squared the equation, all answers MUST be verified in the original equation. if m = 5 LS = √(5-1) + 5 = 2 + 5 = 7 RS = 5...
October 7, 2014

Pre-Calc/Trig..
how about y = 2x^2 + 3
October 7, 2014

Algebra
Let the length parallel to the house be y let each of the other two equal sides be x 2x + y = 120 y = 120 - 2x Area = xy = x(120 - 2x) or -2x^2 + 120x b) you want the vertex. x of the vertex is -120/(-4) = 30 when x = 30 y = 60 Maximum area = xy = 1800 ft^2
October 7, 2014

Algebra
so 0 = -2.7t^2 + 6 t^2 = 6/2.7 t = √(6/2.7) or appr 1.49 seconds
October 7, 2014

@ Brady math(fractions)
There is no need to find common denominators when either multiplying or dividing fractions You only need to do that when adding or subtracting them
October 7, 2014

Calculus
I made a sketch showing the distance covered by the plane after it passed over the kangaroo as x miles let the angle of elevation be Ø I have : tanØ = 2/x xtanØ = 2 x sec^2 Ø dØ/dt + tanØ dx/dt = 0 when the distance between the ...
October 7, 2014

Calculus help please
sin^-1 (2/7) means, find the angle Ø , so that sinØ = 2/7 sketch a right-angled triangle with base angle Ø, opposite side 2 and hyptenuse 7 by Pythagoras, adj^2 + 2^2 = 7^2 adjacent = √45 = 3√5 then tanØ = 2/(3√5) thus tan(sin^-1 (...
October 7, 2014

MATH
this problem consists of finding the vertex of the parabola, the x of the vertex is -b/(2a) = -40/-8 = 5 when x = 5 A = -4(25) + 40(5) = 100 So the maximum area is 100 ft^2 , when the width is 5 ft. I would suggest you have your caps lock fixed on your keyboard, it will be so ...
October 7, 2014

Math
depends if you round to the nearest tenth or the nearest hundredth to the nearest tenth it would be 1.6 for the nearest hundredth, the above is correct as 1.65
October 7, 2014

calculus 1
sin(anything) has a minimum of -1 and a max of +1 so 18sin(7t) has a min of -18 and a max of 18 since 18sin(7t) is added to 100 the minimum would be 100-18 or 82 the maximum would be 100+18 = 118 period of the function : 2π/7 = period period = appr .897 sec per period so ...
October 7, 2014

math
short piece --- x long piece ---- 9x x + 9x = 20 10x=20 x=2 the short piece is 2 m the long piece is 18 m
October 7, 2014

MATH
tan(x)sin(2x) = √3 sin (x) tanx(2sinxcosx) = √3sinx divide by sinx 2tanxcosx = √3 2(sinx/cosx)(cosx) = √3 sinx = √3/2 I recognize x as one of the special angles, x = 60° but sine is also positive in quadrant II so x = 180-60 = 120° x = 60&...
October 7, 2014

Calculus
cos−1(x) refers to an angle, let's call it Ø , so that cosØ = x = x/1 so sketch a right-angled triangle, label the base angle Ø, it's adjacent side as 1, and its hypotenuse as x then the other side is √(1 - x^2) and cotØ = x/&#...
October 7, 2014

AP Calculus
Darn!!! last line, forgot the +1 , but you figured that out, didn't you?
October 7, 2014

AP Calculus
sometimes called: find the derivative from First Priciples f(x) = 1/√x + x f(x+h) = 1/√(x+h) + x+h f'(x) = Lim ( f(x+h) - f(x) )/h , as h --->0 = lim( 1/√(x+h) + x+h - (1/√x + x )/h as h--->0 = lim ( (1/√(x+h) - 1/√x)/h + h/h) as h...
October 7, 2014

Maths
j : m : s = 12 : 5 : 1 or 12k : 5k : k there are 66 more juices than soft drinks 12k = k + 66 k = 6 milk = m = 5k = 30 30 cartons of milk check if k=6, we have 72 juices, 30 milk and 6 soft drinks 66 more juices than soft drinks ? , yes ratio: 72 : 30 : 6 = 12 : 5 : 1 , yes
October 7, 2014

Maths
boys -- b girls -- g b/g = 3/5 5b = 3g b = 3g/5 OR g = 5b/3 men --- m women -- w m/w = 3/1 m = 3w equation #1: 2/9 of the visitors were children: b+g = (2/9)( b+g+m+w) 9b + 9g = 2b + 2g + 2m + 2w) 7b + 7g = 2m + 2w 7(3g/5) + 7g = 6w + 2w times 5 21g + 35g = 40w 56g = 40w...
October 7, 2014

Math
According to the diagram I drew .... width --- w 5.5(2w) + .5w = 60.375 11.5w = 60.375 w = 5.25 or 5 1/4 ft
October 7, 2014

bank loans
I don't think any bank in 2014 would use simple interest, but anyway .... interest = 3000(18/12)(.12) = $540 (here is where the flaw comes in using simple interest. The $540 would be the simple interest on the full amount of $3000, but the balance is constantly decreasing ...
October 7, 2014

statistics
prob = C(12,3) x C(40,2)/C(52,5) = 220(780)/2598960 = 55/833 or appr .066
October 6, 2014

Math Question
I will assume you meant f(x) = -5√(-4x+4) + 2 or else they would have just added the 2 to the 4 y = -5√(-4x+4) + 2 = -10√(1-x) + 2 , I factored out √4 which is 2 inverse: interchange x and y variables x = -10√1-y) + 2 solve this new equation for y...
October 6, 2014

Math
1 inch = 2.54 cm then 5/6 inches = (5/16)(2.54) cm = appr .794 cm = 7.94 mm , yes it will fit but very loosely 2nd way 2.54 cm = 1 inch 1 cm = 1/2.54 10 mm = 1/2.54 inches 5 mm = 1/5.08 inche = appr .1969 inches which is less than 5/16 inches so it will fit, but just as loose ...
October 6, 2014

Math
yes
October 6, 2014

Pre-Calc/Trig...
vertex form: y = - (x-4)^2 + 4 your text or your notes should have the definitions and properties of that form
October 6, 2014

math
Think! It can't be isosceles, you would need two equal sides. It is not right-angled or else 8^2 would have to be equal to 6^2 + 3^2 definition of scale: a triangle with all sides different.
October 6, 2014

Math
72 ft, 10 inches = 72.8333... ft cos 57 = base/72.8333.. base = 72.8333..(cos 57°) = appr 39.668 ft so I would pick D, 40 ft
October 6, 2014

Algebra
√( (x-7)^2 + (0-6)^2 ) = 10 square both sides and expand x^2 - 14x + 49 + 36 = 100 x^2 - 14x - 15 = 0 (x - 15)(x + 1) = 0 x = 15 or x = -1 interpret my results.
October 6, 2014

Math, ASAP Please
Think about it 5% on $100 would be $5.00 so on a $1000 it would be $50 since it is a bit more than 5% , the only logical choice is $52.50
October 6, 2014

Rational Functions
x-intercept of 3 ---> needs a multiplier of x-3 vertical asymtote of x = -2 ----> needs a divisor of x+2 so far y = (x-3)/(x+2) horizontal asymptote of y = 2 lets slap a 2 infront y = 2(x-3)/(x+2) , as x gets huge y ---> 2 , ( try x = 100,000 ) we want y-intercept of...
October 6, 2014

trig
I assume you made a diagram Because of the symmetry, let's just look at the top part of the diagram Let the centre of the smaller circle be O and the centre of the larger circle be P Let the point of contact of the belt to the smaller circle be A and to the larger circle B...
October 6, 2014

Math
Did you enter 2.98333 , which was my answer using linear approximation method ? , (we can't use a calculator for this)
October 5, 2014

Math
What is the least common multiple (LCM) of 15 and 12 ?
October 5, 2014

Math
Did you look at my previous answer to this problem? Why are you changing names? http://www.jiskha.com/display.cgi?id=1412554250
October 5, 2014

finding the interest
You probably want to use Ms Sue's answer. I did not read the question carefully and read it as finding the interest rate.
October 5, 2014

finding the interest
So loan = 450-90 = 360 let the monthly rate be r 22.8( 1 - (1+r)^-20)/r = 360 1 - (1+r)^-20 = 360r/22.8 very difficult equation to solve, I will use Wolfram http://www.wolframalpha.com/input/?i=solve+1+-+%281%2Br%29%5E-20+%3D+360r%2F22.8 using the logical answer of r = ....
October 5, 2014

Statistics
prob(odd on blue) = 1/2 prob(5 or 6 on yello) = 2/6 = 1/3 prob(odd on blue AND 5or6 on yellow) = (1/2)(1/3) = 1/6 Proof and check: There are 36 possible ways for the 2 dice to fall the ones you want are: 1 5 1 6 3 5 3 6 5 5 5 6, which is 6 of them so prob(as stated) = 6/36 = 1/6
October 5, 2014

Math
If we let L(x) represent the linear approximation for some value of x L(a) = f(a) + f'(a)/(x-a) , were a is a number for which I know the value of f(a) so for √8.9 I know that √9 = 3 , so let a = 9 f(9) = √9 = 3 for f(x) = √x = x^(1/2) f'(x) - (...
October 5, 2014

ALGEBRA
equation #1: |3x-1| + 7 = 2 |3x-1| = -5 but by definition, the |anything| cannot be negative, the same is true for the 2nd equation. So neither one has a solution
October 5, 2014

Math Check
I answered a similar question yesterday http://www.jiskha.com/display.cgi?id=1412431497 The way you placed your brackets, none of your choices are correct
October 5, 2014

Math
at a time of t min, height of water level = h, radius of water level = r V = (1/3)πr^2 h by ratios: r/h = 10/22 = 5/11 11r = 5h r = (5h/11) V = (1/3)π(25h^2/121)h = (25/363)π h^3 dV/dt = (25/121)π h^2 dh/dt given: dV/dt = 30 ft^3/min find: dh/dt when h = 14...
October 5, 2014

Math
Most questions of this type appear to disregard pressure, so in the following solution I will do the same (physics expert will surely groan) V = (4/3)π r^3 dV/dt = 4πr^2 dr/dt so when r = 5 and dr/dt = -12 dV/dt = 4π(25)(-12) = appr -3769.91118
October 5, 2014

Math
at a time of t min, let the height of the water level be h m, and the radius of the water level be r m By ratios: r/h = 4.5/9 = 1/2 2r = h or r = h/2 Volume of cone = (1/3)π r^2 h = (1/3)π (h/2)^2 h = (1/12)π h^3 dV/dt = (1/4)π h^2 dh/dt given: when h = 4 m...
October 5, 2014

Algebra
by definition: p-10 = 20 OR -p+10 = 20 p = 30 or -p = 10 p = 30 or p = -10
October 4, 2014

Math
-80=8b-15+5b -80 + 15 = 13b or 13b = -65 b = -5 Solving an equation means finding that value of the variable which makes the original equation a true statement. We found that value to be b = 5 Now sub that value into the left side and the right side of the ORIGINAL equation. ...
October 4, 2014

Math Help
should have noted that the original function is only valid for x ≤ 1
October 4, 2014

Math Help
I will assume you meant f(x) = -5√(-4x+4) + 2 or else they would have just added the 2 to the 4 y = -5√(-4x+4) + 2 = -10√(1-x) + 2 , I factored out √4 which is 2 inverse: interchange x and y variables x = -10√1-y) + 2 solve this new equation for y...
October 4, 2014

Pre-Calc
number of apples processed = P(22) = .... do the arithmetic cost = C(P(22)) = put the answer of P(22) into C(n)
October 4, 2014

Math
I assume you meant √(21x) , and not the way you typed since 21 = 3x7 , you want either another 3 or 7 in x so that we have at least one perfect square. none of the first 3 choices contain a 3 or 7 ,but 54 does so √(21x54) = √3x7x3x9x2) = √(81*14) = 9&#...
October 4, 2014

Math
sum of all exterior angles of an n-gon is 360 so 360/n = appr 30 n = 12 It is a 12-gon
October 3, 2014

Math
sum of angles of a regular polygon = 180(n-2) so 180(n-2)/n = 165 180n - 360 = 165n 15n = 360 n = 24 sum of inside angles = 180(22) = 3960°
October 3, 2014

Math
sum of interior angles of a heptagon = 5(180) = 900 so we have 520 + x + x + (3/2)x = 900 2x + 1.5x = 380 x = appr 108.57° take it from here
October 3, 2014

(MCV4U) Vectors
ignore the first part of my solution, start with My diagram ...
October 3, 2014

(MCV4U) Vectors
Since you labeled your subject as vectors I will use them let the wind vector be (rcosØ, rsinØ (rcosØ, rsinØ) + (200cos180,200sin180) = (180cos170,180sin170) ( rcosØ, rsinØ) = (22.7346 , 31.2567) 2r^2 = 22.7346^2 + 31.2567^2 r = 27....
October 3, 2014

Algebra
6x/16 + 1/16 = (6x+1)/16
October 3, 2014

Math
Are you sure the sum of the other two regions is 25a and not 24a ? then the sum of the area would be a^2 + 144 + 24a = (a+12)^2 which would make it a square of sides a+12 for a perimeter of 4a + 48
October 3, 2014

math
2 chicken lay 8 eggs in 3 days 1 chicken lays 4 eggs in 3 days 1 chicken lays 8 eggs in 6 days 5 chicken lay 40 eggs in 6 days
October 3, 2014

5th grade math
16/5 - 2 = 6/5 (6/5)/2 = 3/5 or 60%
October 3, 2014

math
(x+2y)^2 = (x+2y)(x+2y) = x^2 + 2xy + 2xy + 4y^2 = x^2 + 4xy + 4y^2 The method I used is sometimes referred to a FOIL
October 3, 2014

Pre-Calc/Trig...
You are correct
October 3, 2014

Analytic Geometry CHECK MY ANSWER
the slope is (6-3)/(2-2) = 3/0 which would be undefined. None of the choices are correct Your line is a vertical line.
October 3, 2014

Analytic Geometry CHECK MY ANSWER
your equation should read: t = 85n + 25 Doesn't the value of t "depend" on what you put in for n ?? So t would be the "dependent" variable, so that implies that ....... your choice of answer makes no sense. You mean to say that the total t is not ...
October 3, 2014

Pre-Calc/Trig...
yes and yes
October 3, 2014

Pre-Calc/Trig...
how about letting t = 1, 2, 3, 4, ... minutes and then interpret the results. What do you notice about the distance for every minute of change in time.
October 3, 2014

Pre Calc
so you want: 7000(1.07^t) = 1400 1.07^t = 2 take log of both sides, and by the rules of logs t log 1.07 = log 2 t = log2/log1.07 = appr 10.245 years
October 3, 2014

Pre-Calc/Trig...
so in f(x) = 1/(x+2) you are replacing x with 3+h so f(3+h) = 1/(3+h + 2) = 1/(h+5)
October 3, 2014

Algebra 1 Check
correct do you know why ?
October 3, 2014

Math Questions
I will do the first one: 6√24x = 18√24 divide by √24 6x = 18 x = 3 do the others the same way, #1 and #3 are incorrect, you had #2 correct btw, I interpreted you question as you typed it. I assume you did not mean 6√(24x)
October 3, 2014

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