Tuesday
August 4, 2015

Posts by Reiny


Total # Posts: 30,540

math
first: length -- 3x width --- 2x area = 6x^2 2nd: ??? "The ratio of the length of the larger is 7:5" don't know what that means
February 11, 2015

Math
a) you would simply choose 3 of the 11 = C(11,3) = 165 b) 3 men of 5, 4 women of 6 = C(5,3) x C(6,4) = 10x15 = 150
February 11, 2015

Math (Interest)
yes, it would be 18.6387 since the time is so short, it is no surprise that the two answers are the same
February 11, 2015

Math (Interest)
don't make it look so complicated i = .025/12 = .00208333.. (I use my calculator's memory to store such numbers, don't round them off yet) amount = 18.6(1.00208333...)^1 , for 1 month = 18.6(1.00208333.. = $ 18.64 Wow, we gained 4 cents interest !
February 11, 2015

Algebra
let x^(1/4) = k then we have k^2 - 7k + 12 = 0 (k-3)(k-4) = 0 k = 3 or k = 4 x^(1/4) = 3 or x^(1/4) = 4 x = 81 or x = 256
February 11, 2015

perpendicular vectors
Nice !
February 11, 2015

linear algebra
I will read that as [(a -b) -3] = [7 (a+b)] then a-b=7 a+b=-3 add them 2a = 4 a = 2 and then 2+b=-3 b = -5
February 11, 2015

MATH
100^2 ÷ 10^-5 = 10^4/10^-5 = 10^9 , which is 1 billion times as large
February 11, 2015

math
width -- x length -- 2x+1 x+x + 2x+1 + 2x+1 = 29 6x+2=29 take over Just realized I used x instead of w, no big deal.
February 11, 2015

Algebra 1
width --- x length --- 2x+4 (17)(x)(2x+4) = 2720 x(2x+4) = 160 2x^2 + 4x - 160=0 x^2 + 2x - 80 = 0 (x+10)(x-8) = 0 x = -10 , which would make no sense or x = 8 The box is 8 inches wide check: w=8 l= 20 h=17 V = 8x20x17=2720 All looks good
February 11, 2015

Algebra
I suggest googling "factoring trinomials" or "factoring quadratic trinomials" Also there are many good youtubes and Khanacademy has many clips to show you how.
February 11, 2015

Algebra
if you mean factored form, then = (2x+1)(3x+2)
February 11, 2015

Algebra 1
there is no solution in the set of real numbers, but there are two complex number solutions. see: http://www.jiskha.com/display.cgi?id=1362104847
February 11, 2015

Algebra 1
there are two solutions x^2 + 6x + 5 = 0 (x+1)(x+5) = 0 x = -1 , you had that one or x = -5
February 11, 2015

Algebra 1
take 1/2 of the middle term coefficient and square that number (1/2)(11 = 11/2 squared gives us 121/4 so x^2 + 11x + 121/4 = (x+11/2)^2 so n = 121/4 or 30.25 if you want a decimal
February 11, 2015

algebra
let her initial speed be x mph time for first trip = 320/x new speed = x+10 mph time for second part of trip = 500/(x+10) so.. 500/(x+10) - 320/x = 2 times x(x+10) 500x - 320(x+10) = 2x(x+10) 500x - 320x - 3200 = 2x^2 + 20x 2x^2 - 160x + 3200 = 0 x^2 - 80x + 1600 = 0 (x-40^2...
February 11, 2015

math
.342 = 342/1000 so its reciprocal is 1000/342 = 500/171
February 11, 2015

Math - Answer Check
all your answers are correct
February 11, 2015

Algebra
suppose something costs $x and you increase it by 5% doing it your ways: increase = .05x end result = x + .05x = x(1 + .05) = 1.05x so you get the result after anything is increased by 5% , just multiply by 1.05 or to get the result after anything is increased by 16% , just ...
February 11, 2015

maths
The LCM of 2, 3, 5, 7, and 12 is 420 So they will all fire together again 420 minutes, or 7 hours from now
February 11, 2015

math
Ok, I made a sketch and concluded that the angle at X is 150° Is there another question?
February 11, 2015

Andrew , Meg, Sarah - math
We are not going to do your assignment/homework for you. What have you learned from my previous answers so far?
February 11, 2015

math
same stuff (any reason why you switched names ?)
February 11, 2015

math
use the concepts I used in my previous answer to your similar question.
February 11, 2015

math
how about y = 3x^2/( (x-3)(x-6) )
February 11, 2015

math
Did you mean y = (3x+6)/(x-7) ?? Vertical asymptotes: What happens when the denominator is zero? For what value of x does this happen ? horizontal : Which terms fall by the wayside as x→∞ ? what remains of y = (3x ...)/(x ....) ?
February 11, 2015

math
by the "just look at it" theorem lim x→∞ sqrt(x^2+9) = x , so there is no limit e.g. let x = 1,000,000 ,using my calculator I got 1,000,000
February 11, 2015

math
I am sure you meant: lim (2- e^x)/(2+9e^x) divide each by e^x = Lim (2/e^x - 1)/(2/e^x + 9) now as x→∞ , e^x ---> 0 and we approach the value (0-1)/(0+9) = -1/9
February 11, 2015

math
area of original = 40(20) =800 cm^2 after cutoff, new size is 32 by 12 area of that = 32(12) = 384 cm^2 area of strip cut out = 800-384 = 416 cm^2
February 11, 2015

maths(Probability)
There are 36 ways for the 2 dice to fall (make yourself a 6by6 matrix) a) there is only one way to get a sum of 2 ---> 1,1 prob (a sum of 2) = 1/36 b) a sum of 7: 1 6, 2 5, 3 4, 4 3, 5 2, 6 1, so 6 ways prob(a sum of 7) = 6/36 = 1/6 c) a prime: the primes are 2, 3, 5, 7, or...
February 11, 2015

math
actually it should be -2 notice that x ---> negative infinity, so the x^3 is negative
February 11, 2015

Calc
There is no "formal" way to do this. One method is Newton's Method if you know Calculus Another way is to have a good calculator, and finetune your values of x e.g. let x = 1 LS = e^1 = 2.71828.. Rs = 4 let x = 2 LS = e^2 = 738 RS = 6 , ahh, I went too high let x...
February 11, 2015

Algebra 1
teams left after 1 week = 64 = 128(1/2) teams left after 2 weeks = 32 = 128(1/2)^2 .. teams left after 6 weeks = 128(1/2)6 = 2
February 11, 2015

math101
I will assume compound interest: 6900(1.12)^n = 9384 (1.12)^n = .1.36 take log of both sides, and use log rules nlog1.12 = log1.36 n = log1.36/log1.12 = 2.7 it would take 2 years and appr. 8.5 months check: balance after 1 year = 6900(1.12) = 7740.32 balance after 2 years = ...
February 11, 2015

Math
Did you make your sketch? area of larger square = (2s)^2 = 4s^2 For the side of the smaller square: x^2 = s^2 + s^2 x = √2s area of smaller is (√2s)^2 = 2s^2 so the ratio of their areas = 4s^2 : 2s^2 = 2 : 1
February 10, 2015

algebra
number of quarters --- x number of dimes ---- 2x number of nickels ---- 2x+47 25x + (10)(2x) + 5(2x+47) = 400 solve for x, then sub into my definitions
February 10, 2015

algebra
let the amount of pure acid added be x ml x + .45(600) = .5(x+600 x + 270 = .5x + 300 .5x = 30 x = 60
February 10, 2015

Math
no, it said that she flew at 800 mph for one hour, so she used up 1 hour of flying time To average 1000 mph in flying 1000 miles would take exactly one hour, which she has already spent flying. So she must do the remaining 200 miles in zero time. That is why it is not possible.
February 10, 2015

Math
She must fly faster than the speed of light, that is, it can't be done. I want your explanation of why I said that.
February 10, 2015

math - exponent laws
You must be referring to the post from yesterday where you had -( -11/-17)^-10 ÷ (9/5)^(1/10) http://www.jiskha.com/display.cgi?id=1423540960yes , you could have done that. I treated the (-11/-17)^-10 as 1/(11/17)^10 which was 77.725... You want to do (17/11)^10 which ...
February 10, 2015

Algebra 1
outer area = (10x+89)(7x+7)= 70x^2 + 693x + 623 skylight area = (x+5)(3x+3)= 3x^2 + 18x + 15 remaining area = 70x^2+693x+623 - (3x^2+18x+15) = 67x^2 + 675x + 608
February 10, 2015

Algebra 2
first of all notice that each term divides by 2, so (6x^2+4x-16)/(2x-2) = (3x^2 + 2x-8)/(x-1) hard to show the actual long division on here but you should get 3x+5 with a remainder of -3
February 10, 2015

Algebra 2
factor it, you are looking at the difference of squares x^4 - 81 = 0 (x^2 + 9)(x^ - 9) = 0 , and again (x^2 + 9)(x+3)(x-3)= 0 x= -3 or x = +3 or x^2 = -9 ---> x = ± 3i If you have not studied complex numbers, then just go with the x = ± 3
February 10, 2015

math
if that is supposed to say u^2 - 14u + 49 , then can you think of two numbers which multiply to get 49 and have a sum of -14 ? -7 and -7 come to mind = (u - 7)(u - 7) or (u-7)^2
February 10, 2015

Math
volume is proportional to the cube of their corresponding sides V/280 = 2.5^3/1^3 V = 280(15.625) = 4375 cm^3
February 10, 2015

Algebra
area of first = x^2 area of 2nd = (x+5)^2 x^2 + x^2 + 10x + 25 = 193 2x^2 + 10x - 168 = 0 x^2 + 5x - 84 = 0 (x - 7)(x + 12) = 0 x = 7 or x = -12 , which would be a silly square the first square is 7 by 7 the second is 12 by 12 check: 49 + 144 = 193 , yeahhh!
February 10, 2015

math
The following OA , OB etc are vectors OA + AB = OB AB = OB - OA AB = OB + AO = (4,1,-3) + (-3,2,-1) = (1,3,-4) |AB| = √(1^2 + 3^2 + (-4)^2) = √26 = appr 5.10
February 10, 2015

Math
the the two integers be x and y x+y = 100 y = 100-x product = xy = x(100-x) 100x - x^2 ≥ 2000 x^2 - 100x + 2000≤0 so we are looking for all those integer values of x where the parabola y = x^2 - 100x + 2000 lie below the x-axis, so we have to find the x-intercepts ...
February 10, 2015

Math
For some unit of time: number of words for kala --- 4x number of words for rose ---- x but x = 48, so kala typed 192 words Since Lita typed twice as fast as kala, lita typed 384 words
February 10, 2015

Maths
Rather tedious to find the inverse of a 4by4 matrix, and out of the question to type it all out. Surely you can find an inverse calculator on the web. Just google and pick one then multiply that inverse by 5 8 12 7
February 10, 2015

Math
I just did this before you decided to repost under a different name
February 10, 2015

maths
sin30° = height/10 height = 10sin30 = ...
February 10, 2015

Trigonometry
I made a sketch and marked all the angles Let r be the distance between start and ending point. the angle between the two trips is 90+28°20'+28°20' = 146° 40' by the cosine law: r^2 = 86^2 + 124^2 - 2(86)(124)cos146°40' = 40591.28405 r = √...
February 10, 2015

math
if the base is a proper fraction (less than one) and you are raising it to positive exponents > 1, the answer is less than the base if the base is a improper fraction (greater than one) and you are raising it to positive exponents > 1, the answer is greater than the base...
February 10, 2015

Calculus
I will answer no more of these types until you show me some of your efforts and work
February 9, 2015

Calculus
these questions you are posting all basically all the same. a = 72 v = 72t+c when t = 0 , v = 17 17 = 0 + c, v = 72t + 17 s = 36t^2 + 17t + k when t = 0 , s = 10 so k = 10 s = 36t^2 + 17t + 10
February 9, 2015

Calculus
see http://www.jiskha.com/display.cgi?id=1423541938 and make the necessary adjustments
February 9, 2015

Calculus
height = -16t^2 + 96t v = -32t + 96 = 0 at the top 32t=96 t = 3 it will take 3 seconds to reach the max, and that max is -16(9) + 96(3) = 144 ft
February 9, 2015

MATH - exponent laws
-(11/17^-10/(9/5)^(1/10) use the y^x key, the most powerful key on your calculator (-11/-17)^-10 = 1/(11/17)^10 = 77.725... (I stored that in A on my calculator) (9/5)^(1/10) = 1.0605.. so -(11/17^-10/(9/5)^(1/10) = -77.725... /1.0605... = -73.28837824 I use the memories on my...
February 9, 2015

Math
What is 360 ÷ 18 what is 5 times that ?
February 9, 2015

Math
Not necessarily. The angles could be different, thus not similar Imagine the second figure having hinges at the vertices and you "squish" the figure.
February 9, 2015

Math
I am guilty of that more often than you are
February 9, 2015

Math
prob of making the free throw = 32/60 = 8/15 so the prob of NOT making it = 1 - 8/15 = 7/15
February 9, 2015

Math 110
can't make out a) if x5/3 is supposed to mean x^(5/3) use the notation I just used.
February 9, 2015

Math
a peek at the graph might guide you along http://www.wolframalpha.com/input/?i=plot+y+%3D++2x+%2B+1+%E2%88%92+sin%28x%29
February 9, 2015

Mat104
i = .055/3 = .018333... what is 955(1.018333..)^12 ?
February 9, 2015

Calculus
sketching should have been no problem both have axes on the x-axis, one has vertex (-49,0) and opens to the right the other has vertex (49,0) and opens to the left There is perfect symmetry and they meet at (0,7) and (0,-7) I would take horizontal slices, thus integrate with ...
February 9, 2015

math
gradient = slope = dy/dx dy/dx = 3ax^2 - 6x - 2 using the given: 7 = 3a(1) -6(1) - 2 7 = 3a - 8 3a = 15 a = 5
February 9, 2015

Calculus
well, finding y' and y'' is really the main part of the meal, the rest is just cleaning the dishes. you should know the derivatives of the 6 basic trig functions by heart. y' = secx(sec^2 x) + tanx(secxtanx) , by the product rule = sec^3 x + tan^2 x secx y'...
February 9, 2015

Math
a = -32 v = -32t + c since it was 'dropped' , when t=0 , v =0 so c = 0 v = -32t 120 = -32t t= 120/-32 = -15/4 s = -16t^2 + k when it hit the ground, t = 15/4 , s = 0 0 = -16(225/16) = k k = 225 s = -16t^2 + 225 So the height of the cliff is 225 ft
February 9, 2015

Differentiation
y' = (e^tanx )(sec^2 x)
February 9, 2015

Vector Cross & Dot Product
1. I got (-1,2,6) Your error is in the last calculation, I had 4(1) - (2(-1) = 6 and then (-1,2,6)dot((-1,0,3) = 1 + 0 + 18 = 19 2. since this problem depends on your answer from #1, check your calculations with the correct answer from #1, I did get (6,-3,2)
February 9, 2015

Cross Product of Vectors
your initial vector is correct magnitude of (0,6,18) = √(0+36+324) = √360 = 6√10 so I see that your unit vector is also correct Perhaps you are looking at some answer key and the answer there looks different. They might have rationalized the denominator 1/&#...
February 9, 2015

math
Ms Sue correctly assumed that the largest rectangle one can have for a given perimeter is a square, and gave you a correct solution based on that assumption. Were you supposed to find the answer without making that assumption? Let me know and I will show you how.
February 9, 2015

math
What is the USE format ?
February 9, 2015

Math
yes, but that would give you how many brought skates, which is not the question. First, how many came ? (3/4) of 400 = 300 of those 1/5 brought skates number who brought skates = (1/5)(300) = 60 Assuming the rest rented skates, so 300-60 or 240 rented skates or if 1/5 brought ...
February 9, 2015

Trigonometry
since 1+cot^2theta=csc^2theta cot^2 Ø = csc^2 - 1 = (-3.589142)^2 - 1 = 11.8819403 cotØ = ± √11.8819403 = ± 3.447... but since Ø in in III, cotØ must be positive, so cotØ = 3.447.. Why were you doing 1/sin(-3.58914...
February 9, 2015

Algebra 2
(1 - √(3x)/√(6x) = (1 - √(3x)/√(6x) * √(6x)/√(6x) = (√(6x) - (√18)x)/(6x) = ( √(6x) - 3√2 x)/(6x)
February 9, 2015

Algebra 2
Follow the same steps suggested by Steve in your previous post or take the negative term to the right side, then square collect all like terms, isolate the square root term and square again.
February 9, 2015

Math - not PSC
y1/x1 = y2/x2 65/33 = y2/44 y2 = 44(65/33) = 260/3 or 86 2/3 = appr 86.67 or "If y is directly proportional to x" means y = kx if y = 65, x = 33 65 = 33k k = 65/33 y = (65/33)x when x = 44 y = (65/33)(44) = appr 86.67
February 9, 2015

math
If the base is a square of area 49, then each side is 7 cm so look at the block, you have 2 squares + 4 equal surfaces on the sides Surface area = 2(49) + 4(7)(10) = 378 cm^2 btw, I don't understand your previous post, it looks incomplete
February 9, 2015

linear algebra
I will give you 2 nice youtubes to show how this is done https://www.youtube.com/watch?v=taBHTo8sviM She sets it up nicely, but does not actually show how to find the determinant of a 3by3. This one shows a nice short-cut method to find the determinant, but I must point out ...
February 9, 2015

Math- Calculus
1. done by just getting a "feel" for the numbers e^(-2x) = 1/e^(2x) so as x ---> infinitity, the denominator gets huge and the result approaches zero as for the sinx it simply runs up and down between -1 and 1 no matter what x is or how large x is So the lim(e^(-...
February 9, 2015

Calc
1. lim tanx/x , as x ---> 0 (after each line below) = lim (sinx/cosx)/x = lim (sinx/x)(1/cox = lim sinx/x * lim 1/cosx , you should know these = (1)(1) = 1 2. y = x^2 dy/dx = 2x Let the point of contact be (a,b) we know b = a^2 and the slope of the tangent is 2a but using ...
February 9, 2015

math
Same as the standard "hand-shake" problem number of games = 10 choose 2 = C(10,2) = 45 In the hand-shake problem, we have 10 people and they all shake hands on meeting. so each of the 10 people can shake hands with 9 others for 90 shakes but that would include A ...
February 9, 2015

Algebra 1
#1, your middle term is -x , thus A #2 D #3 B How are you doing these, so far they are all wrong (4p-2)(p-4) = 4p^2 - 16p - 2p + 8 = 4p^2 - 18p + 8 #4 A = 2πr^2 + 2πrh = 2π(3x-2)^2 + 2π(3x-2)(x+3) = 2π[ 9x^2 - 6x - 6x + 4 + 3x^2 + 9x - 2x - 6] = 2π...
February 9, 2015

math algebra
In the golden rectangle the ratio of length : width = (1+√5) : 2 or appr 1.618 5/w = (1+√5)/2 w = 10/(1+√5) = appr 3.09 check: 5/3.09 = appr 1.6181.. good enough
February 9, 2015

Maths
8m, 9 cm = 809 cm number of pieces which are 9 cm long = 809/9 = 89.88.. or appr 90 cm each btw, in the true usage of the metric system, one would not say 8m, 9cm it would be either 809 cm or 8.09 m the beauty of the metric system is that you don't have to mix units like ...
February 9, 2015

math
number without a 1 = 9^7 = 4,782,969 so number where no 1 occurs = 4,782,969 number where a 1 does occur = 10,000,000-4,782,969 = 5,217,031 Your conclusion ?
February 9, 2015

Geometry
Use the information from my previous post to answer this one. Let me know what your answer is
February 9, 2015

Geometry
Since perimeter is a linear relationship, the ratio of perimeters of two similar figures is proportional to the ratio of their sides, thus 48 : 54 or 8 : 9 Since area is a quadratic relationship , ..... the square of their sides, thus 48^2 : 54^2 = 2304 : 2916 = 64 : 81
February 9, 2015

math
I assume you want this in simple interest. let the amount needed now be A A + A(.0547)(8/12) = 1762 A + A(.0364666..) = 1762 A(1.0364666..) = 1762 A = 1762/1.0364666.. = $1700.00
February 8, 2015

Calculus
just tedious work .... I suggest you make a sketch, and plot the points (0,20) , (2,22), .... you will get trapezoids by joining all the y-values and drawing in all the verticals look at the first trapezoid, its base = 2 the left vertical is 20 and the right vertical is 22 ...
February 8, 2015

math1979
Wow, let me know what stock that is. profit = 96-17 + 3.57 = 82.57 I = PRT 82.57 = 17(R)(1) R = 82.57/17 = 4.857 = appr 486 %
February 8, 2015

math
In your last line you have a = 30, d = -2 but you had found d = -10, which is correct so a = 30, d = -10 sum(n) = (n/2)(2a + (n-1)d ) , you should know that formula sum(15) = (15/2)(60 + 14(-10)) = -600
February 8, 2015

Math
One of the basic identities you should have at your disposal is sec^2 x = 1 + tan^2 x so sec^2 x + tanx = 1 1 + tan^2 x + tanx = 1 tanx(tanx + 1) = 0 tanx = 0 or tanx = -1 if tanx = 0 then x = 0 or x = 180° if tanx = -1, then x = 135° or x = 315° x = 0 , π , 3...
February 8, 2015

Math
f ' (x) = ax^(a-1)(1-x)^b + b(1-x)^(b-1) x^a = 0 for a max of f(x) x^(a-1) (1-x)^(b-1)[a(1-x) + b(x)] = 0 then x^(a-1) = 0 , which is not possible or (1-x)^(b-1) = 0 , which is also not possible or a-ax+bx=0 a = ax+bx a = x(a+b) x = a/(a+b) f(a/(a+b))) = [a/(a+b)]^a [(1-a...
February 8, 2015

Vectors/Scalars?
The dot product is an operation between any two vectors and is always a scalar, your (u dot v)dot (a dot c) = (a scalar) dot (a scalar) which would be undefined, since there is no such thing as a dot product between two scalars.
February 8, 2015

Math 1105
18x^2+36x+18 = 18(x^2 + 2x + 1) = 18(x+1)^2 so one square is x+1 by x+1, the other is 3√2 by 3√2
February 8, 2015

Math
what I stated is true for any positive base > 1 thus it is true for 9^x
February 8, 2015

  1. Pages:
  2. <<Prev
  3. 8
  4. 9
  5. 10
  6. 11
  7. 12
  8. 13
  9. 14
  10. 15
  11. 16
  12. 17
  13. 18
  14. 19
  15. 20
  16. 21
  17. 22
  18. Next>>

Members