Monday
October 20, 2014

Posts by Reiny


Total # Posts: 27,484

math
Your statement is false (25+5)(25-5) ≠ 0 it is (30)(20) = 600 What were you trying to do? To "solve" an equation, it must contain a variable Your expression shows the "difference of squares" could be done as 25^ - 5^2 = 625 - 25 = 600
July 11, 2014

College Algebra
What about it ? did you mean (15x^2-23x-21) / (3x-7) ? are we graphing y = (15x^2-23x-21) / (3x-7) ? are we solving (15x^2-23x-21) / (3x-7) = 0 ?
July 10, 2014

math
I would let the width = x then the length is x+120 and x(x+120) = 6400 x^2 + 120x - 6400 = 0 which factors to (x-40)(x+ 160) = 0 x =40 or x = -160, which is not possible, can't have negative width width is 40, length is 40+120 = 160 check: area = 40(160) = 6400 , yup!!
July 10, 2014

math
I will assume you mean (3x-4)/(4x+2) use the quotient rule ... y = (3x-4)/(4x+2) dy/dx = ( (4x+2)(3) - (3x-4)(4) )/(4x+2)^2 = (12x + 6 - 12x + 16)/(4x+2)^2 = 22/(4x+2)^2 or = 11/(2(2x+1)^2)
July 10, 2014

Math
correct, assuming that repetition of letters and numbers is allowed
July 9, 2014

Algebra
really ? isn't x^2 a perfect square? isn't 121 a perfect square ? ---- 11^2 = 121 Don't we subtract (-) to take the difference between 2 numbers? Now what do you think??
July 9, 2014

algebra
http://www.wolframalpha.com/input/?i=plot+4y%3Dx%2B8%2C+x%3D2%2F3y%2B2
July 9, 2014

Statistics/Probability
prob(Saturday) = 1/7 prob(not Saturday) = 6/7 prob(exactly 4 of 15 years is a Saturday) = C(15,4) (1/7)^4 (6/7)^11 = appr .1043 at least 2 Saturdays ----> 1 - (case of 0 Saturday + case of 1 Saturday) = 1 - (6/7)^15 - C(15,1)(1/7)(6/7)^14 = .6534 check my arithmetic
July 9, 2014

Algebra II
I will assume p5 is meant to be p^5 and 2x2 is meant to be 2x^2 , then p^5 + 2x^2 + 3px + 17 = 0 2x^2 + 3px + p^5 + 17 = 0 a quadratic with a = 2 , b = 3p and c = p^5 + 17 for real roots: 9p^2 - 4(2)(p^5 + 17) ≥ 0 9p^2 - 8p^5 - 136 ≥ 0 using Wolfram to solve, I got...
July 9, 2014

precalculus
make a sketch of the positions at t = 0, 1, 2, 3, and 4 and you will see that you need something like height = 5sin(π/2)t + 8 to meet your condition of 6:00 o'clock position being 3 m we do a 1 second shift to the right, height = 5sin [(π/2)(t-1)] + 8 check: when...
July 9, 2014

math
prob(male) = .4 prob(female) = .6 prob(5 of 6 are male) = C(6,5) (.4)^5 (.6) = ... prob(at least 4 of the 6 are boys) = prob(4 boys) + prob(5 boys) + prob(6 boy s) = C(6,4) (.4)^4 (.6)^2 + C(6,5) (.4)^5 (.6) + .4^6 = --- all boys = .4^6
July 9, 2014

Algebra
first of all, write it in its general form ax^2 + bx + c = 0 t^2 - 6t + 3 = 0 a = 1, b = -6 , c = 3 t = (-b ±√(b^2-4ac) )/(2a) = (6 ± √(36-4(1)(3))/2 = (6 ± √24)/2 = (6 ± 2√6)/2 = 3 ± √6 No complex roots here.
July 8, 2014

Math
let me guess, you want to know the speed of the east-bound ship. looks like a Pythagorean problem: (24(22.2))^2 + (24t)^2 = 863^2 ..... see if you can get appr 28.28 km/h
July 8, 2014

math
a+3d = -3 a+8d = 12 subtract: 5d = 15 d = 15/5 = 3 a + 9 = -3 a = -12 common difference is 3 sum(7) = (7/2)(-24 + 6(3)) = -21
July 8, 2014

trigo
slope of y = -mx is -m, but m is a positive number, so the slope is negative the slope is also equal to tan Ø the tangent is negative in quadrants II and IV, but x > 0 in IV so 270° < Ø < 360°
July 8, 2014

math
√3 is an irrational number, which is a subset of the real numbers
July 8, 2014

math
salary in 1st year --- x salary in 3rd year = x(1.03)^2 salary in 4th year = x(1.03)^2 (1.05) salary in 5th year = x(1.03)^2 (1.05)^2 x(1.03)^2 (1.05)^2 = 100000 x = 100000/((1.03)^2 (1.05)^2) = $87,180.84
July 8, 2014

Algebra
hint: How many wheels does a tricycle have ? how many wheels does a bicycle have? tri ?? bi ??
July 7, 2014

Math
amount = 500( 1.08^8 - 1)/.08 = ....
July 7, 2014

math
.10(1) + .025(1) = x(2) same type as your previous post, I will let you finish it.
July 7, 2014

math
.02(25) + .06(35) = x(60) 2.6 = 60x x = 2.6/60 = .04333.. The resulting concentration is 4 1/3 %
July 7, 2014

maths
assuming that all available digits must be used at least once: largest : 44210 smallest: 1024 now multiply them
July 6, 2014

math
width --- p length -- p+1 p(p+1) = 6 p^2 + p - 6 = 0 easy to solve by factoring...
July 6, 2014

math
from smallest to largest of the 7 consecutive EVENS x, x+2, x+4, x+6, x+8, x+10, x+12 middle is x+6 x+6 = 48 x= 42 smallest is 42
July 6, 2014

Math
Using Calculus .... x+y = 11 ---> y = 11-x S = 1/x - 1/y = 1/x - 1/(11-x) = x^-1 - (11-x)^-1 dS/dx = -1/x^2 - 1/(11-x)^2 = 0 for a max/min of S -1/(11-x)^2 = 1/x^2 -x^2 = 11-x^2 -2x^2 = 11 x^2 = -11/2 No real solution , there is no maximum see Wolfram http://www....
July 5, 2014

math
Looking back I see many posts by you involving the quadratic equation and its properties, You have shown no sign that you have attempted any of them, nor did you indicate where your problems lie. The intent of this forum is not to simply do homework or assignments for you. for...
July 5, 2014

maths
I suspect a typo, since I get 2/(x+p ) = 1/r x+p = 2r ---> linear equation x = 2r-p , which only has one root
July 5, 2014

maths
For any quadratic, complex roots or irrational roots always come as conjugate pairs so if one root is 2 + i√3, the other must be 2 - i√3 sum of those roots = 4 product of those roots = 4 - 3i^2 = 7 In any quadratic of the form x^2 + px + q = 0 the sum of roots = -p...
July 5, 2014

math
first reduce the equation to x + 6y - 3 = 0 Since the new line is perpendicular, it must be 6x - y + c = 0 plug in (2,4) 12 - 4 + c = 0 c = -8 new equation: 6x - y - 8 = 0
July 5, 2014

maths
Since in a square, the diagonals bisect each other, 5x+9 = 5+3x 2x = -4 x = -2
July 5, 2014

maths
the quadratic must have been (x-tan30)(x-tan15) = 0 x^2 - xtan30 - xtan15 + tan30tan15 = 0 x^2 + x(-tan30 - tan15) + tan30tan15 = 0 comparing this to x^2 + px + q = 0 p = -tan30 - tan15 and q = tan30tan15 then 2 + q - p = 2 + tan30tan15 - (-tan30 - tan15) = 2 + tan30tan15 + ...
July 5, 2014

maths
let the roots of the first be s and 4r let the roots of the second be s and 3r 1st: x^2 - 6x + a = 0 sum of roots = 6 product of roots = a s+4r = 6 and 4rs = a 2nd: x^2 - cx + 6 = 0 sum of roots = c product of roots = 6 s+3r =c and 3rs = 6 ---> rs = 2 so in 4rs = a , we ...
July 5, 2014

maths
Sachins would have been (x-4)(x-3) = 0 x^2 - 7x + 12 = 0 Rahul's would have been (x-3)(x-2) = 0 x^2 - 5x + 6 = 0 Sachin was wrong with the 12, should have been 6 Rahul was wrong with the -5x , should have been -7x Equation should have been x^2 - 7x + 6 = 0 (x-6)(x-1) = 0 x...
July 5, 2014

algebra
amount of the 30% solution needed ---- x L amount of the 16% solution needed --- 5-x L .3x + .16(5-x) = .272(5) times 100 30x + 16(5-x) = 136 30x +80 - 16x = 136 14x = 56 x = 4 L 4 L of the 30%, and 1 L of the 16% solution would be needed.
July 5, 2014

math
For any linear equation in the form Ax + By + C = 0 , the slope is -A/B So for both of your equations, the slope is -1/3 thus they are parallel
July 5, 2014

Algebra
For a complicated equation such as yours, the most powerful method is probably Newton's Method. let y = 3x^2+4lnx+4 dy/dx = 6x + 4/x newx = x - y/(dy/dx) = x - (3x^2+4lnx+4)/(6x + 4/x) which simplifies to newx = (3x^2 - 4lnx)/(6x + 4/x) now use an iteration process, I ...
July 3, 2014

algebra
Vikky, what Steve is telling you that complex roots, as well as irrational roots, always come in conjugate pairs. e.g. if one root is 5 - 7i, then there has to be a matching 5 + 7i e.g. if one root is (4 + 3√5)/2 , then there has to be a (4 - 3√5)/2 So, if you know...
July 2, 2014

math
Using a ruler and compass, draw the base line of 9 inches. Set your compass to 6 inches, from the left end of the base draw an arc above the base line. Set your compass to 4 inches, from the right end of the base, draw an arc above the base line The intersection of the two ...
July 2, 2014

Math
To be an arithmetic progression, (2t-1) - t = (2t+4) - (2t-1) solve for t
July 2, 2014

math
what is 60 + (2/5)(60) ?
July 2, 2014

algebra math
I don't see any obvious relationship, nor does Wolfram http://www.wolframalpha.com/input/?i=plot+%7B%282%2C3%29%284%2C5%29%286%2C4%29%288%2C6%29%2810%2C5%29%2812%2C12%29%2814%2C16%29%2816%2C22%29%2818%2C26%29%2820%2C32%29%7D
July 2, 2014

mat/simultaneous equation
I would use elimination here 1st times 3 ---> 6x - 15y = 39 2nd times 5 --> 25x - 15y = -75 subtract them: -19x = 114 x = -6 back into 1st -12 - 5y = 13 -5y = 25 y = -5 x = -6 , y = -5
June 29, 2014

calculus
Assuming we take the growth to be exponential , ... 5 e^(28r) = 7.5 e^(28r) = 1.5 ln both sides ln (e^(28r)) = ln1.5 28r = ln 1.5 r = .0145 the rate is 1.45% check: 5 e^(28*.0145) = 7.5
June 27, 2014

maths probability
Answered by MathMate a few days ago under a Physics heading http://www.jiskha.com/display.cgi?id=1403632512
June 27, 2014

math
In a 32:3 ratio, there are 35 parts 7 m or 700 cm divided by 35 = 20 cm by part So what do you think?
June 27, 2014

Math
I get 3t-9-20t+15 = 5-42t-7 25t = -8 t = -8/25
June 26, 2014

Math
I will assume you mean 120a^4b^2/(-24a^9b^-15) if so, then it would be -5 a^-13 b^17 or -5b^17/a^13
June 26, 2014

Algebra 1
Use this notation to indicate exponents: x^3 - x^2 - 4x + 4 = 0 grouping will work x^2(x - 1) - 4(x - 1) = 0 (x-1)(x^2 - 4) = 0 (x-1)(x+2)(x-2) = 0 so x = 1 , -2 , +2
June 26, 2014

Algebra
yes
June 26, 2014

calcus
Isn't that just a straight-forward Pythagorean calculation? Surely somebody who studies Calculus MUST know how to do that. Let me know where your problem lies.
June 26, 2014

maths
Again, having a hard time trying to establish the order of operation. e.g. #3 I put it into Wolfram the way you typed it , and the webpage interpreted it the same way I did http://www.wolframalpha.com/input/?i=+X%5Elogx%2B5%2F3%3D+10%5E5%2Blog+x What a messy equation that ...
June 26, 2014

maths
1. by definition of logs x^2 - 12x + 36 = 10^2 (x-6)^2 = 100 x-6 = ±√100 = ±10 x = 6 ± 10 = 16 or -4 2. you have the product of 3 numbers = 0 so one of them is zero but log4 and log2 are non-zero real numbers, so log2x must be 0 that is, x = 1 3.not ...
June 26, 2014

maths
11^(1/2) = √11 since 11 is not a perfect square, 11^(1/2) is irrational
June 26, 2014

maths
1st number --- x 2nd number -- 8-x sum of squares = x^2 + (8-x)^2 = x^2 + 64 - 16x + x^2 = 2x^2 - 16x + 64 d(sum of squares)/dx = 4x - 16 = 0 for max/min 4x=16 x = 4 the two numbers are both 4 check: for the answer, sum of squares = 16+16 = 32 let 1st be 3.99, the other 4.01 ...
June 26, 2014

math
first you need the monthly payment. i = .11/12= .00916666.. n = 12 Paym (1 - 1.0091666..^-12)/.009166.. = 15000 paym = 1325.72 Here are my titles to the amortization table ( they will not line up niceley) Time - payment - interest - repayment - balance now -- 0.00 -- 0.00 -- 0...
June 26, 2014

math
prob = C(4,3)*C(4,3)/C(52,6) = 16/20,358,520 4/5089630
June 25, 2014

math-Ms Sue please help
I am pretty sure that for loans lasting 25 years, compound interest would be used. i = .10/12 = .008333... n = 25(12) = 300 payment( 1 - 1.008333^-300)/.0083333) = 73700 I get payment = $ 669.71
June 24, 2014

math
All your questions deal with the use of our 4 basic compound interest formulas. What exactly do you not understand about these questions ? They all are very straight forward.
June 24, 2014

math
i = .08/12 = .006666.. n = 18(12) = 216 amount = 225( 1.00666..^216 - 1)/.00666.. = ... you do the button pushing
June 24, 2014

math
amount(1.02)^12 = 15000 amount = 11827.40
June 24, 2014

math
amount after 3 years at 5% pa compounded semiannually = 4494(1.025)^6 = 5211.66 so interest = 5211.66-4494 = 717.66
June 24, 2014

math
how about y = x^3/(x-1) confirmed: http://www.wolframalpha.com/input/?i=plot+y+%3D+x%5E3%2F%28x-1%29
June 23, 2014

algebra
√50 = √25√2 = 5√2, which is choice A
June 23, 2014

MAT 221
-10 < -2 + 8x < 22 add 2 -8 < 8x < 24 divide by +8 , (no change in inequality sign) -1 < x < 3 Can't make out your symbols in the 2nd e.g. use <= for ≤ and >= for ≥
June 23, 2014

Frequency
assuming that they either supported it or not supported it, P(E) = 80/400 = 1/5
June 22, 2014

Algebra
yes, I would put your answer in set form, using { } brackets, eg. range = {2,-5}
June 21, 2014

Trigonometry help
Depends on the interpretation of "makes a 15° angle with the boat". If the rope makes a 15° angle with the water line, (parallel to the bottom of the boat) you would have: depth/24 = cos 75° or depth/24 = sin 15° , both giving you depth = 6.21 If the ...
June 21, 2014

Math
1 term(n) = ar^(n-1) term(10) = 16(-1/2)^9 = 16(-1/512) = - 1/32 2. ar^9 = 3/512 ar^14 = 3/16384 divide the 2nd by the first r^5 = 1/32 r = 1/2 back into the first a(1/2)^9 = 3/512 a(1/512) = 3/512 a = 3(512)/512 = 3
June 18, 2014

Math
looks like an arithmetic sequence with d = 17 and term2 = -243 a+d = -243 a = - 260 term(67) = a+66d = -260 + 66(17) = ... you should have at your finger-tips the formulas for the sum of n terms you have the a and the d, so plug in
June 18, 2014

oops - finite math
that should be .25 + .47 for OR the way I had it would have been for AND
June 17, 2014

finite math
what is .25(.47) ?
June 17, 2014

finite math
How many of the 59 homeruns went to left field ?
June 17, 2014

geometry
Did you carefully read the question ?
June 17, 2014

geometry
let me rephrase the question ... what is the greatest common factor of 720, 1008, and 672 ? 720 = 8*9*10 = 16*3*3*5 1008 = 8*9*14 = 16*3*3*7 672 = 16*3*2*7 so who is common? looks like 16*3 or 48 check: 720/48 = 15 1008/48 = 21 672/48 = 14 , nothing common in any of those 3 ...
June 17, 2014

Math
well, let's put z=2 into the 2nd z=y + 2 = 5 y = 3 So now we know that z=2 and y = 3 now into the 1st: x - 6 + 2 = 8 z = 12 So, where was your problem with this ? Looks very very easy.
June 17, 2014

Math
use term(n) = a + (n-1)d here a = -847 , d = 11 , n = ?? , and term(n) = -11 solve : -11 = -847 + (n-1)(11) which should be pretty straightforward to do.
June 17, 2014

probability and statistics
Ummmh, if everybody got an 85, wouldn't the average be 85 ??? , so mean = 85 and since nobody "deviated" from that score, wouldn't the standard deviation be zero ????
June 17, 2014

Math
It must be true that (2x-1) - (3x-2) = (4x-3) - (2x-1) -x + 1 = 2x - 2 -3x = -3 x = 1 check: terms would be 1 , 1, 1 strange sequence but it is arithmetic
June 17, 2014

Math
so you are adding 64 + 81 + 98 + ... for 17 terms a = 64 d = 17 n = 17 use the formula Sum(17) = (17/2)[128 + 16(17)] = 3400
June 17, 2014

algebra
so -2x^2 + 8x + 5 = 0 x^2 - 4x = 5/2 complete the square ... x^2 - 4x + 4 = 5/2 + 4 (x-2)^2 = 13/2 = 26/4 x-2 = √26/4 ........ since √26 is close to 5 x = appr 2 ± 5/2 = appr 4.5 or .5
June 17, 2014

Math
I saw this question and have not been able to get a handle on it we know that ln(x) has an expansion formula http://upload.wikimedia.org/math/6/d/b/6dbf56b2e5f34d298c1e71ddd93b3448.png but it only good for |x-1| < 1 so we could create a series of terms = 1/(x+1) ( (x-1) - (...
June 17, 2014

geometry
let the mean be x (1/8) / x = x / (8/32) x^2 = (1/8)(8/32) x^2 = 1/32 x = ± 1/√32 or ± 1/(4√2) or ± √2/8
June 17, 2014

Math
a=2 ,d=4 term(12) = a+11d = 2 + 44 = 46
June 17, 2014

Math
a = x-y d = 2x+y-3 just use your formula term(101) = a + 100d = x-y + 100(2x+y-3) = x-y + 200x + 100y - 300 = 201x + 99y - 300
June 17, 2014

Maths
You will need brackets to properly identify the order of operations. you probably mean : 5/(1/2) + 14( 5/(1/2) + 14)(1/4) which is 10 + 14(10+14)/4 = 10 + 60 = 70 As to the relationship between the two number ??? yes, you are right, they are both whole numbers or they are both...
June 17, 2014

Math
surface area = 2π(2.5)^2 + 2π(2.5)(9) = ---
June 17, 2014

MATH
Your solution is illustrated by http://www.google.com/search?q=intersection+of+3+planes&tbm=isch&imgil=VKeuvId73BKgcM%253A%253Bhttp%253A%252F%252Ft2.gstatic.com%252Fimages%253Fq%253Dtbn%253AANd9GcTP5OK2B8xVEFseHgCh5S25ao2K4pX-fClEpupY9ltfPRK6cZC8NA%253B332%253B265%...
June 17, 2014

MATH
if you divide the 2nd by 2, all your equations start with 2x. That is good, since we could add or subtract them to eliminate the x 2x+y-3z=4 2x+z=10 -2x+3y-13z=-8 subtract 1st from the 2nd -y + 4z = 6 , #4 add the 2nd and 3rd 3y - 12z = 2 , #5 #4 times 3---> -3y + 12z = 18...
June 17, 2014

algebra
Did you mean, are the lines through each pair of points parallel or perpendicular to each other ?
June 17, 2014

Angles,Lines and Triangles
let the angles be x and y x+y = 116 x-y = 24 add them 2x = 140 x = 70 then y = 46 one angle is 70°, the other is 46° leaving 64° for the third angle
June 17, 2014

math
use a simple ratio ... miles/7 = 64/80 miles = 7(64/80) = 5.6
June 17, 2014

Math
since it is parallel to y=x/2 + 4 it will differ only in the y-intercept, so let y=x/2 + b plug in the point(10,12) 12 = 5+b b = 7 y = x/2 + 7
June 16, 2014

algebra 2
Since you labeled it algebra rather than Calculus, I will use an algebraic solution, completing the square h(t) = -16(t^2 - 9t + 81/4 - 81/4) + 24 = -16( (t - 9/2)^2 - 81/4) + 24 = -16(t - 9/2)^2 + 324 + 24 = -16(t-9/2)^2 + 348 this is a downwards-opening parabola with vertex...
June 16, 2014

Math
#1 and #2 are the same type as the ones I just did for you Give them a try #3 a=2 , d=4 a+(n-1)d = term(n) 2 + (n-1)(4) = 106 2 + 4n - 4 = 106 4n = 108 n = 27 term(27) = 106
June 15, 2014

Math
common difference = 4+p - (6-p) = 4+p - 6 + p = 2p - 2 term(101) = a+100d = 6-p + 100(2p-2) = 6-p + 200p - 200 = 199p - 194
June 15, 2014

Math
a+32d = -2p a+ 60d = 26p subtract: 28d = 28p d = p a + 32p = -2p a = -34p
June 15, 2014

Maths
R(t) = e^kt, where R(t) is the percentage remaining after t t years, k is a constant given: when t = 50 , R(50) = .6 .6 = e^(50k) ln both sides ln.6 = 50k lne k = ln.6/50 R(t) = e^( (ln.6/50) t)
June 15, 2014

Math
volume = h(50-2h)^2
June 15, 2014

add maths
OP /PA = 1/3 3OP = AP now follow the same method I just showed you in your previous post
June 14, 2014

add maths
let the point be P(x,y) then PA = 2PB √( (x-1)^2 + y^2) = 2√( (x+2)^2 + y^2) square both sides and expand x^2 - 2x + 1 + y^2 = 4(x^2 + 4x + 4 + y^2) x^2 - 2x + 1 + y^2 = 4x^2 + 16x + 16 + 4y^2 3x^2 + 18x + 3y^2 = -15 x^2 + 6x + y^2 = -5 complete the square: x^2 + ...
June 14, 2014

Pages: <<Prev | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | Next>>

Search
Members