Friday
December 19, 2014

Posts by Reiny


Total # Posts: 28,259

MATH 101
not enough information. is f(x) linear ? we must assume that, since you only have 2 points, namely, (3,0) and (-4,0) slope = 0/-7 = 0 so we have a horizontal line and f(x) = 0 f(x) is the x-axis
November 16, 2014

math
let's look at x^2 + 2x + 4 = 0 by completing the square, (in this case the easiest way to solve it) x^2 + 2x = -4 x^2 + 2x + 1 = -4+1 (x+1)^2 = -3 but anything squared cannot be negative, so there is no real solution consider y = x^2 + 2x + 4 this parabola never touches or...
November 16, 2014

Math
let f(x) = 3x^3 + 2x^2-1 f(1) = 3 + 2 - 1 ≠ 0 f(-1) = -3 + 2 - 1 ≠ 0 f(1/3) = 1/9 + 2/9 - 1 ≠ 0 f(-1/3) ≠ 0 So there are no "nice" roots looking at the graph, there appears to be a real solution at appr x = 0.5 and two complex roots (the graph...
November 16, 2014

CAL
y = x^3/x- x would reduce to y = x^2 - x and (1,-2/3) would NOT lie on this curve. So there is something wrong with the way you typed it Use brackets to establish the correct form Otherwise this question is bogus.
November 16, 2014

CAL
could be the way you typed your equation. The way you typed it, why not just simplify x^3/x to x^2 ? That is why I am suspicious about the way it was typed. Did you mean y = x^(3/x) - x ?
November 16, 2014

Derivative
But, to even attempt this question, you MUST know the derivatives of the basic trig functions. in this case, use the quotient rule dy/dx = ( (1+sinx)(-sinx) - cosx(cosx) )/(1+sinx)^2 = (-sinx - sin^2 x - cos^2 x)/(1+sinx)^2 = (-sinx -1)(1+sinx)^2 = -(1+sinx)/(1+sinx)^2 = -1/(1...
November 16, 2014

calculus
#1, your dy/dt is correct b) correct, to the right when v(t) > 0 but they probably want to know when that happens look at your derivative, the denominator will always be positive, since it is something squared. So the ± of your v(t) is only determined by the ...
November 16, 2014

Calculus Help
It is not a matter of "choosing" here, you must calculate it. f ' (x) = cos(7-5x)(-5) = -5cos(7-5x) f '(π) = -5cos(7-5π) = 5cos(-8.7078..) = 3.770 Did you set your calculator to radians in your DRG mode ?
November 16, 2014

Pre Albergra
Just put on my tin-foil hat and got a message of 3.4 cm How did I do ?
November 16, 2014

Calculus
let x = √5 then x^2 - 5 let y = x^2 - 5 y' = 2x Newton said: newx = x - y/y' = x - (x^2 - 5)/(2x) = (2x^2 - x^2 + 5)/2x = (x^2 + 5)/(2x) x newx 3 2.3333.... 2.333... 2.23809... 2.23809... 2.23606... could have stopped here 2.23606.. 2.236067878 2.236067978.. 2....
November 16, 2014

Trig
The primary function is ln(...) we can only take logs of positive numbers now look at the sine curve only, and note where it lies above the x-axis so the intervals would be 0 < x < 90° or 360° < x < 450° or 720° < x < 810° or ... how about...
November 16, 2014

Math
first , because of the negatiave outer exponent = 1/(16x^2)^3/4 since (ab)^x = a^x * a^x we get 1/( (16^(3/4 ) * x^(3/2) now 16^(3/4) = (16^(1/4) )^3 = 2^3 = 8 so finally = 1/(8 (√x)^3 )
November 16, 2014

math
Volume of cylinder = π r^2 h you are given r and h, plug in the values and evaluate
November 16, 2014

Elementary Math
Ricardo --- x years Miriana ---- x+4 Ten years ago: Ricardo --- x-10 Miriam --- x+4 - 10 = x-6 x-6 = 3(x-10) easy to solve ... let me know what you get
November 16, 2014

Math
One would think that after trying this for two days, you might realize that you don't have enough information. e.g. If your tank is a large rectangular tank of 10 ft by 10 ft the water level would rise more than if your "tank" had been a swimming pool.
November 16, 2014

Math
PV = 800( 1 - 1.09^-10)/.09 Wow, let me know which bank pays you 9% in 2014.
November 16, 2014

Advanced Algebra (Infinite Geometric Series)
8.690909.... =8.6 + .09 + .0009 + .000009+... = 86/10 + .09/(1-.01) = 86/10 + .09/.99 = 86/10 + 9/99 = 86/10 + 1/11 = 478/55
November 15, 2014

Math
2 / ((cos(r^2 - s^2) / (sin(r^2 - s^2)) = 2 * (sin(r^2 - s^2) / (cos(r^2 - s^2) = 2 tan (r^2 - s^2)
November 14, 2014

Math Please Assist
sin^3 x + sinx cos^2 x = cosx sinx(sin^2 x + cos^2 x) = cosx sinx (1) = cosx sinx/cosx = 1 tanx = 1 x = 45° or x = 225° but you wanted to be between 0 and 180 so x = 45°
November 14, 2014

math
since you want cos 2Ø in terms of x from x+5 = 9sinØ bringing the 5 over would make things worse ... and no, you would not distribute the 9 over the 9sinØ - 5 I would proceed this way: sinØ = ( x+5)/9 now you will have to use one of the half-angle ...
November 14, 2014

Pre-Calc/Trig
quadratic --- x^2 term makes it that linear ----- x term makes it that cubic ------ from the x^3 term the highest exponent term establishes what kind it is
November 14, 2014

Algebra
slope = (-3-1)/(1-3) = 2 so it has to be one of the last two of your choices sub in (1,3) into y = 2x+5 ---> doesn't work sub in (1,3) into y = 2x - 5 ----> Yeahhh! so y = 2x-5 that is what bob had suggested to you, that is, try the points in the equations.
November 14, 2014

math
so in effect the ship went 41 + 15 or 56 north and 23 east. so d^2 = 56^2 + 23^2 = 3665 d =√3665 = 60.5 km
November 14, 2014

math probability
since the code > 400, your choice for the first digit is 6, you can put 10 different digits in the 2nd spot, and 10 different digits in the 3rd spot number of possible codes = 6x10x10 = 600 this would include 400, which cannot be used, since it must be greater than 400 so ...
November 14, 2014

Math
to the nearest 10 13---> 10 46 ---> 50 87 ---> 90 sum = 150 if you added them up like you did to get 146 , you have the actual answer, why bother estimating ? Besides, 146 rounded to the nearest tens is 150, not 160
November 14, 2014

math probability
I don't understand the question. In your first sentence, you are saying that there are only 9 dollars in the box.
November 14, 2014

Intermediate Algebra
simple interest formula: I = PRT, lets plug in our values 85 = 6000(R)(1/12) multiply both sides by 12 1020 = 6000R divide both sides by 6000 R = 1020/6000 = .17 or 17% You had the correct answer, but you should not just piece-meal bits and pieces from the equation.
November 14, 2014

Intermediate Algebra
sloppy use of the decimal place and your solution makes absolutely no sense. if x is the amount loaned at 6% ... .06x + .14(15000-x) = 1500 .06x + 2100 - .14x = 1500 -.08x = -600 x = 600/.08 = 7500 So $ 7500 was loaned at 6% and $7500 at 14% check: .06(7500) + .14(7500) = 1500
November 14, 2014

MATH
true if both are positve, or if both are negative. depends if one is + , the other - e.g 8/5 - 9/7 = 11/35 but 15/4 - 3/2 = 9/4 , still a mixed number
November 13, 2014

Geometry
let the size of the cut-out be x by x inches length of base = 24-2x width of base = 24-2x height = x V = x(24-x)^2 = x(576 - 48x + x^2) =576x - 48x^2 + x^2 dV/dx = 576 - 96x + 3x^2 = 0 for a max of V x^2 - 32x + 192 = 0 (x - 24)(x - 8) = 0 x - 8 or x = 24, but if x = 24, we ...
November 13, 2014

Probability.. HELP!
what is 36x35x34 ? Do you know why ?
November 13, 2014

Math, Please Help!
I will assume we are not distinguishing between small and capital letters. I will do one: TENNESSEE - 9 total, 2 N's , 4 E's, 2 S's total number of ways = 9!/(2!4!2!) = 3780 Can you see what I did ? OHIO ----> 4!/(2!) = 12 try the others.
November 13, 2014

College Algebra
If you mean (-10-6i) /( -9+9i) , then the brackets are essential (-10-6i) /( -9+9i) = (-10-6i) /( -9+9i) * (-9-9i)/(-9-9i) = (90 + 90i + 54i + 36i^2)/(81 -81i^2) = (54 + 144i)/162 = 1/3 + (8/9)i
November 13, 2014

College Algebra
type it this way: (-6 - √10)/(3 + 8√10) I will assume you are rationalizing (-6 - √10)/(3 + 8√10) = (-6 - √10)/(3 + 8√10) * (3 - 8√10)/(3 - 8√10) = (-18 + 48√10 - 3√10 + 80)/(9 - 640) = ( 62 + 45√10)/-631 = (-62...
November 13, 2014

Calculus
are you using the usual notation so that a(t) is acceleration, v(t) is velocity and s(t) is distance ?? I will assume you are a(t) = t^2 - 8t + 5 v(t) = (1/3)t^3 - 4t^2 + 5t + c s(t) = (1/12)t^4 - (4/3)t^3 + (5/2)t^2 + ct + k s(0) = 0 0-0+0+0+k=0 k=0 s(1) = 20 1/12 - 4/3 + 5/2...
November 13, 2014

algebra
looks like we are dividing by -2 each time, so ....
November 13, 2014

algebra
So a is always positive and b is always negative. What is a positive divided by a negative ?
November 13, 2014

Algebra
if f(x) = 4x^7+x^5+3x^2-2x+c f(-1) = -4 -1 + 3 +2 +c = 0 c = 0
November 13, 2014

math
Since the area of each time is 16 in^2, each side of the tile must be 4 inches the table is 6 ft by 6ft or 72 inches by 72 inches so we need 72/4 or 18 tiles along a side. since the table is square, the number of tiles needed = 18(18) 324 tiles
November 13, 2014

Math
I usually get rid of nasty decimals ... .1g+3.75m=7.36 --> 10g + 375m = 736 --> g = (736-375m)/10 8.2g+21m=73 ----> 82g + 210m = 730 10g +375m = 736 -times 410 --> 4100g + 153750m = 301760 82g + 210m = 730 -times 50 --> 4100g + 10500m = 36500 subtract them: ...
November 13, 2014

math
I think Bob has a typo in dividing x+y+z by 2 instead of 3 x+y+z+ (x+y+z)/3=360 3x+3y+3z + x+y+z = 1080 4x+4y+4z = 1080 x+y+z = 270
November 13, 2014

Algebra 2
3x^2 - 24x + 45 = 0 remember Steve told you about all that "zero stuff" ? divide each term by 3 x^2 - 8x + 15 = 0 can you think of 2 numbers that add up to -8 and multiply to get 15 ? I am thinking -3 and -5 so (x-3)(x-5) = 0 x-3=0 ----> x = 3 or x-5 = 0 ----> ...
November 13, 2014

math
Proof for all values: let a+b+c+d+e = S let M be the average M = S/5 5M = S then S/M = 5/1 or S : M = 5 : 1
November 13, 2014

Math
correct
November 13, 2014

algebra. help!
first one: y = 2^x why did you possible pick c) not a single one of the pairs given satisfies that equation. It is clearly y = (x+3)^2 , that is, d)
November 13, 2014

Algebra
number of $1 --- n number of $2 --- n+11 number of $3 --- n-18 now for the "value" : 1n + 2(n+11) + 3(n-18) = 100 n+2n+22 + 3n-54 = 100 6n = 132 n = 22 then n+11 = 33 n-18 = 4 so 22 $1 bills , 33 $2 bills and 4 $3 bills check: 22 + 66 + 12 = 100 Yeahh
November 13, 2014

Algebra
surely you can replace x with 2 and add 2+6
November 13, 2014

Algebra
in h(x) = −9x^3+3x^2−2x+2 they are in order of decreasing degree
November 13, 2014

Algebra
h(x) = −9x^3+3x^2−2x+2 why did you put commas between terms in your answer ?
November 13, 2014

math
cost = 16m + 1895 , where m is the number of miles and cost is in cents 16m + 1895 = 5000 16m = 3105 m = appr 194 miles check: 194(.16) + 18.95 = 49.99
November 13, 2014

Algebra 2
As Morgan pointed out, your left side is a perfect square (x+4)^2 = 16/9 x+4 = ± 4/3 x = 4/3 - 4 = -8/3 or x = -4/3 - 4 = -16/3 your signs were wrong
November 13, 2014

algebra
tom has x stickers Matt has 6x stickers there must have been a total of 140 stickers x + 6x = 140 7x = 140 x = 20 Tom has 20 and Matt has 120 So Matt has to give 50 of them to Tom check: Tom: 20+50 = 70 Matt: 120-50 = 70 Yeahhh
November 13, 2014

Trig/Pre-Calc
try x = ±1 , ±2, ±4, ±8 I got x = 8 to work for me so after a sythetic division, I got (x-8)(15x^2 + x - 2) = 0 (x-8)(3x-1)(5x + 2) = 0 x = 8 , 1/3 , -2/5
November 13, 2014

math
same type of problem as your previous one
November 13, 2014

math
What is 9 ÷ (3/8) ?
November 13, 2014

chin
That is a "serious" problem I will use A for ace F for facecard and L for non-ace, non-face (L for loser) I will also assume that none of the 4 cards drawn in a game are returned to the deck, but they would be returned after a game is played. so the possible ...
November 13, 2014

maths algebra
I think you are referring to this earlier post by you http://www.jiskha.com/display.cgi?id=1415787409 I agree with Steve's answer, I subbed his answer back in the original equation, and it worked. Steve's solution was correct, perhaps you typed it incorrectly. As to ...
November 13, 2014

math
Just translate the English into Math "Half the total number of balls are pink. " ----> p = (1/2)(r+b+g+p) 2p = r+b+g+p p = r+b+g , #1 "One-fourth of the number of green balls equals one-third of the numher of blue balls. " ----> (1/4)g = (1/3)b 3g = ...
November 13, 2014

Algebra
amount = 19 (1/2)^(150/97) = appr 6.5 g
November 13, 2014

math
look at Steve's solution here http://www.jiskha.com/display.cgi?id=1382123644 then change the numbers to fit your problem
November 12, 2014

math
at a time of t minutes, let the radius of the water level be r cm let the height of the water level be h cm by ratios: r/h = 1.75/6 1.75h = 6r r = 1.75h/6 = 7h/24 V = (1/3)π r^2 h = (1/3)π(49h^2/576)h = (49π/1728) h^3 dV/dt = (49π/576) h^2 dh/dt without ...
November 12, 2014

calculus
total distance = 24 + 24(.95) + 24(.95)^2 + .... an infinite GS, where a = 24 and r = .95 sum(all terms) = a/(1-r) = 24/(1-.95) = 24/.05 = 480 metres
November 12, 2014

Calculus
nope, I have no idea how you got that. use the product rule, y = x secx y' = x(secx)(tanx) + secx or = x(1/cosx)(sinx/cosx) + 1/cosx = xsinx/cos^2 x) + 1/cosx or = (xsinx + cosx)/cos^2 x so slope = (π/4)(√2/2) + √2/2)/(1/2) = .....
November 12, 2014

finance math
Assumption: the rate stays at 7% throughout her 31 years of deposits and the 15 years of withdrawals. (What happens after the 15 years of retirement and her money is used up ? ) let her payment + employers share be $x per year x( 1.07^31 - 1)/.07 = 30000(1 - 1.07^-15)/.07 you ...
November 12, 2014

Math
so in your equation, y is the number of words and x is the number of minutes so set y = 2500 50x - 25 = 2500 50x = 2525 x = 50.5 so it will take 50.5 minutes or 50 minutes and 30 seconds.
November 12, 2014

Algebra
Trish, since subtraction only involves "like" terms, and g(x) does not contain any x^4 term, nothing can happen to the x^4 term of f(x) so your result still contains the x^4 term , and thus is a polynomial of degree 4
November 12, 2014

Math
Well, I would suggest you do each division and see.
November 12, 2014

Math
Your question asked for the slope, you gave the equation as an answer. I can tell that you found the slope to be 35, which is correct. Also the equation is correct
November 12, 2014

Algebra 2
Neither equation you state is a quadratic equation for the first, we could attempt to write it as 0x^2 + 5x - 6 = 0 , but when we attempt to use the formula x = (-b ± √(b^2 - 4ac) )/2a we get x = (-5 ± √(25 - 0)/0 = 0/0 , which of course causes all ...
November 12, 2014

Math
good job !
November 12, 2014

Math
yes, I would get y - 100 = (100/3)(x - 3) times 3 3y - 300 = 100x - 300 100x - 3y = 0 or y = (100/3)x
November 12, 2014

Math
I would simplify that ... 50/1.5 = 100/3 Normally we don't mix decimals with fractions, use either one or the other. your answer technically is correct
November 12, 2014

Algebra
If you were to fully expand this, your unsimplified line would consist of 27 terms - that is, any combination of terms in the first bracket times any term in the second bracket times any term in the third bracket the only way to get x^3 is to have -3 from the first times -3x ...
November 12, 2014

Algebra
so ( p(x) )^3 = (x^4-3x+2)(x^4-3x+2)(x^4-3x+2) now consider which combination can produce a term ending in x^3 ??
November 12, 2014

Algebra
so f(x) has to contain an x^4 term and g(x) does NOT contain an x^4 term so what happens to that x^4 term in f(x) when g(x) is subtracted from it ???
November 12, 2014

math
let the base be x by y m V = (x)(y)(1) = xy xy = 9 y = 9/x cost = 50xy + 60xy + 2(40x) + 2(40y) = 110xy + 80x + 80y = 110x(9/x) + 80x + 720/x = 110 + 80x + 720/x d(cost)/dx = 80 - 720/x^2 = 0 for a min of cost 80x^2 = 720 x^2 = 9 x = 3 then y = 9/3 = 3 the box should be 3 by 3...
November 12, 2014

Math Help!!!
1. 1/2 is rational, thus real (any rational is automatically real) -1.016879413894 --- can't tell from the way it was typed. No repetition is apparent, but no indication is given that it continuous. If it terminates the way it was typed, then it is rational the last two ...
November 12, 2014

Algebra
amount = 4500(1 + .045/365)^3650 = 7057.21 or $ 7057 to the nearest dollar
November 12, 2014

Math
Each of the sides must be 10 m The longer diagonal creates an isosceles triangle with angles 30,30 and 120° Several ways to do this 1. Construct a perpendicular which will bisect the diagonal. Let the diagonal be 2x then x/10 = cos30° x = 10cos30 = 8.66.. 2x = 17.32 m ...
November 12, 2014

ap calc
so far ok -3sin(x)-2cos(x)=0 3sinx = -2cosx sinx/cosx = -2/3 tanx = -2/3 construct your triangles in quad II and IV for both the hypotenuse is √13 in quad II y = 3(-3/√13) - 2(2/√13) = -13/√13 in quad IV y = 3(3/√13) -2(-2/√13) = 13/√...
November 9, 2014

ap calc
First of all, since (1,4) is on the curve, 4 = a + b dy/dx = a - b/x^2 = 0 for a max or min but we are told that this is true when x = 1 so a - b/1 = 0 a - b = 1 add them, 2a = 5 a = 5/2 sub back into the first equation, a+b=4 5/2 + b = 4 b = 3/2 a = 5/2 , b = 3/2
November 9, 2014

Math
by Pythagoras, you can find MW = 12 then cosW = 12/13
November 9, 2014

college algebra
same post
November 9, 2014

college algebra
x^4 +12x^3 +10x^2-9x+9x+22=0 I suspect a typo, why would you have two x terms without combining them?
November 9, 2014

calculus
y' = (4x+3)^5 (-4)(5x+2)^-5 (5) + (5x+2)^-4 (5)(4x+3)^4 (5) = -20(4x+3)^5 (5x+2)^-5 + 20(4x+3)^4 (5x+2)^-4 take it further if there is need by taking out a common factor of 20(4x+3)^4 (5x+2)^-5
November 9, 2014

Math - Word problem
Mary, your problem is a variation of the famous "spider and fly" problem. Here is a webpage that has the same concept, you have an electrical outlet and box instead of spider and fly. http://mathworld.wolfram.com/SpiderandFlyProblem.html Use Steve's instructions ...
November 9, 2014

Algebra 2
you just proved my point, you forgot to switch back to one of your other names
November 9, 2014

Algebra 2
Don't change names, stick to one name follow the same steps I showed you yesterday for the same type of problem http://www.jiskha.com/display.cgi?id=1415491412 expand first, then bring everybody to the left and factor. Remember the right side has to be zero.
November 9, 2014

Algebra 2
follow the same steps I showed you yesterday for the same type of problem http://www.jiskha.com/display.cgi?id=1415491412 expand first, then bring everybody to the left and factor. Remember the right side has to be zero.
November 9, 2014

calculus
follow the steps I just showed you for your previous problem (same thing)
November 9, 2014

calculus
f(f(x)) = f(4x^2 - 1) = 4(x^2 - 1)^2 - 1 don't know if you have to expand that, leave that up to you g(f(x)) = g(4x^2 - 1) = 4/(4x^2 - 1)
November 9, 2014

average
Reverse your thinking. How do you think they found the average of those 4 numbers to be 36 ?
November 9, 2014

Calc
notice the point (4,0) does not lie ON the curve. So your sketch should show that. let that point be (a,b) so we know b = √a or a = b^2 dy/dx = (1/2)x^(-1/2) or 1/(2√x) so at the point (a,b) the slope of the tangent is 1/(2√a) I will use the property that at ...
November 9, 2014

math
number of men --- m number of women --- w number of children --- c m+w+c = 180 , #1 m = 2w , #2 w = 3c , #3 from #2 , w = m/2 then in #3, 3c = w c = (1/3)w = (1/3)(m/2) = m/6 back in #1 m+w+c = 180 m + m/2 + m/6 = 180 times 6 6m + 3m + m = 1080 10m= 1080 m = 108 then w = m/2...
November 9, 2014

Calc
why not just state the equation of the parabola, then we can do the question
November 9, 2014

Algebra
you want g(x) = g(x) , so x^3 + x^2 + x - 1 = x^3 - x^2 + x + 1 2x^2 = 2 x^2 = 1 x = ± 1 if x = 1 , g(1) = 1 - 1 + 1 + 1 = 2 if x = -1 , g(-1) = -1 - 1 - 1 + 1 = -2 so they intersect at (1,2) and (-1,-2)
November 9, 2014

Algebra
Are we to assume that your line AB is a straight line? If so, we can find the slope of AB slope AB = (b^2 -a^2)/(b-a) = (b-a)(b+a)/(b-a) = b+a we can write the equation as y - a^2 = (b+a)(x-a) also (3/2,0) lies on it, so 0-a^2 = (b+a)(-3/2 - a) -a^2 = -3b/2 -ab - 3a/2 - a^2 3b...
November 9, 2014

maths
I made a sketch and it looks like a simple cosine law problem d^2 = 10^2 + 3^2 - 2(10)(3)cos135 = 151.426... d = 12.3 km/hr then to find the small acute angle Ø sinØ/3 = sin 135°/12.3.. sinØ = .1723.. Ø = 9.927° direction is S (45-9.927..)&...
November 9, 2014

Trigonometry
if you want the direct line distance (along the hypotenuse) sin 19.5 = 939/d d = 939/sin19.5 = 2813 m If you want the horizontal displacement tan 19.5 = 939/x x = 939/tan19.5 = 2652 m to the nearest metre
November 8, 2014

Algebra 2
x^2 - 13x +40 = x x^2 - 14x + 40 = 0 (x-10)(x-4) = 0 x = 10 or x = 4
November 8, 2014

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