Monday
December 5, 2016

Posts by Reiny

Total # Posts: 36,897

PreCal
b = -(4-√3) = (-4 + √3) then b^2 = 16 - 8√3 + 3 = 19 - 8√3 Bob had 15-8√3 for that part modify his solution.
October 28, 2016

macomb
You have no exponents in your original question. Ms Sue's answer is correct for the question you typed. did you mean −8^−1 + 8^−2 ? then = 1/-8 + 1/8^2
October 28, 2016

Algebra
You did not post the sequence
October 28, 2016

math
A = 2 pi r (r+h) A = 2π r^2 + 2πrh A - 2πr^2 = 2πrh h = (A - 2πr^2)/(2πr)
October 28, 2016

math
You probably meant to type: y = (2x^2 - 5)/(3x^2 - 4) ok, what about it?
October 28, 2016

Math
I have no idea how you got .1446.. 12% ---> 0.12 17% ---> 0.17 3% ---> 0.03 add them up to get 0.32
October 28, 2016

Math
area = 4(2/3) ft^2 = 8/3 ft^2
October 28, 2016

Math
Both the first and the third are given in terms of the 2nd, so we will let the second be our base variable let the 2nd be x then the first is 3x and the third is 10x 10x - 3x = 1050 7x = 1050 x = 150 sub back into my definitions and add them up
October 27, 2016

Math
Ms Sue's answer is the correct one.
October 26, 2016

Differential calculus
y=(√e^x)/x y = (e^(x/2) )/x dy/dx = (x(1/2)e^(x/2) - e^(x/2) )/x^2 simplify if needed.
October 26, 2016

Differential calculus
what kind of root? square root ? is it √(e^x/x) or (√e^x) / x ?
October 26, 2016

Differential calculus with analytic geometry
xy^2+4y^3=x-2y x(2y)dy/x + y^2 + 12y^2 dy/dx = 1 - 2dy/dx dy/x(2xy + 12y^2 + 2) = 1 - y^2 dy/dx = (1 - y^2)/(2xy + 12y^2 + 2)
October 26, 2016

Math
Use a Venn diagram, put in all the data values, and your answers can just be read from the diagram
October 26, 2016

Calculus
2x^2y-3y^2=-11 4xy + 2x^2 dy/dx - 6y dy/dx = 0 dy/dx(2x^2 - 6y) = -4xy dy/dx = -4xy/(2x^2 - 6y) at (2,-1) dy/dx = -4(2)(-1)/(8 -6(-1)) = 8/14 = 4/7 equation of tangent: y+1 = (4/7)(x - 2) massage it any way you need to
October 26, 2016

Algrebra
To visualize the different cases, why not give yourself an actual point. e.g. 2) let (x,y) = (-4,5) <---- had to be in quadrant II then (-x,y) = (4,5) , which is in first quadrant (x,-y) = (-4,-5) , in the third (-x,-y) = (4,-5) , in the fourth
October 25, 2016

Algebra
number of tens ---- x number of fives ---- x+2 number of twenties -- 2x-3 value equation: 10x + 5(x+2) + 20(2x-3) = 445 10x + 5x + 10 + 40x - 60 = 445 55x = 495 x = 9 sub into my definitions ...
October 25, 2016

Math
each side of the base ---- x ft height of box ------------ y ft x^2 y = 8 y = 8/x^2 cost = 6x^2 + 4xy = 6x^2 + 4x(8/x^2) cost = 6x^2 + 32/x
October 25, 2016

Algebra
second number ----- x first number ------- 2x - 183 solve for x: x + 2x-183 = 1161
October 25, 2016

Math
let the longer piece be x cm then the shorter piece is 14-x cm 14-x = (2/5)x times 5 70 - 5x = 2x 70 = 7x x = 10 the long piece is 10 cm, the shorter is 4 cm check: is 4/10 = 2/5 ? , YES
October 25, 2016

math
Most direct way: The volume of the rock equals the change in the volume of the tank. The change in the height was 4 cm. So the volume of the rock is (9)(15)(4) cm^3 = 540 cm^3 or, along your thinking volume of tank at the start = (9)(15)(8) or 1080 cm^3 volume after rock is ...
October 25, 2016

math
I have no idea what your x and y stand for, but in a rhombus, opposite angles are equal and adjacent angles add up to 180° So the other angle is 130°
October 25, 2016

Math
assuming 30 days in a month ... cost of one can per day from machine = 30(.75) = $22.50 cost using 12-pack = (4.99/12)(30) = 12.48 continue
October 25, 2016

Algebra 1
1. A - wrong 2. C - wrong 3. B - wrong 4. A - wrong How did you get your answers? Where you just guessing?
October 25, 2016

Algebra 1
I don't see any choices or any work Surely you don't expect somebody to just go ahead and do this assignment for you , do you? e.g. what steps would you take to answer the first one?
October 25, 2016

Mathematics
Just use your definitions: "first term of an Arithmetic Progression is -4" --> a=-4 "the 15th term is double the 5th" ---> a+14d = 2(a+4d) a + 14d = 2a + 8d 6d = a 6d = -4 d = -2/3 term 12 = a + 11d = -4 + 11(-2/3) = -25/3 check: is the 15th term ...
October 25, 2016

Algebra Two
2500 + .06s ≥ 3100 , where s is his sales .06s ≥ 600 s ≥ 600/.06 s ≥ 10,000
October 25, 2016

Maths GRE
correct
October 25, 2016

Maths GRE
correct , so D
October 25, 2016

Math
fathers age ---- 8x son's age ----- 3x but 8x = 48 x = 6 so the son is 18 or , just using a ratio .... 48/s = 8/3 8s = 144 s = 144/8 =18
October 25, 2016

math
If PQ = QR , (where P(6,-1), Q(1,3), R(x,8)) √( (3+1)^2 + (1-6)^2) = √( (8-3)^2 + (x-1)^2 ) √41 = √(x^2 - 2x + 26) square both sides 41 = x^2 - 2x + 26 x^2 - 2x - 15 = 0 (x-5)(x+3) = 0 x = 5 or x = -3
October 25, 2016

Math
average hourly change = (-21 - 63)/12 degrees/hr =
October 25, 2016

maths
http://www.jiskha.com/display.cgi?id=1477323150
October 24, 2016

maths
http://www.jiskha.com/display.cgi?id=1477323001
October 24, 2016

maths
I did this for you when you were Saphina AlMatary http://www.jiskha.com/display.cgi?id=1477322557 I gave you a good hint for the second one Did you even look at it?
October 24, 2016

Math
good call Steve! (at least I got the right answer, lol)
October 24, 2016

Math
The largest angle will be opposite the side 28 let it be 2Ø, so each bisected angle is Ø let the bisector form angles A and B along the 28 side, so that A + B = 180° --> B = 180-A and we know sinA = sin(180-A) = sinB let the 28 side be split into x and 28-...
October 24, 2016

maths
To talk about "roots" you need equations, you don't have any. anyway.... for 3x^2 - 6x - 7 = 0 , the sum of the roots is 6/2 or 3 and the product of the roots is -7/3
October 24, 2016

maths
check in your text or in your notes what properties are needed to investigate the nature of the roots. hint: it has to do with the determinant. btw. - I can't make your your last equation.
October 24, 2016

Math
clear case of the cosine law BC^2 = 4^2 + (3√3)^2 - 2(4)(3√3)cos30° carry on
October 24, 2016

maths
There is no unique or best way to solve these. After doing a few you get a "feel" of what to look for. e.g. for your first one, notice that last one says: y - 4z = 25 , so y = 25+4z - could be useful look at the first two, they both have 1x so lets subtract the 2nd ...
October 24, 2016

Math
What is your question? What does "and three points at the time of closing" mean?
October 24, 2016

maths
-did the first one for you - still waiting for your response to the second part of my reply http://www.jiskha.com/display.cgi?id=1477316621
October 24, 2016

Math Check Answers
both are correct
October 24, 2016

correction- math
Sara found the area. You want the perimeter = 2(12.75) + 2(8.25) = ..
October 24, 2016

maths
hard to tell which are your groups of equations.
October 24, 2016

Math Check Answers
answers: #1 - A #2 - D #3 - B
October 24, 2016

maths
x^2 - 6x = x^2 - 6x + 9 - 9 = (x-3)^2 - 9 3x^2 + 20x = 3(x^2 + (20/3)x + 100/9 - 100/9 = 3( (x + 10/3)^2 - 100/9 = 3(x+10/3)^2 - 100/3
October 24, 2016

maths
If the coefficient of x^2 is 1, look for 2 numbers which when multiplied give you the constant, and which when added give you the coefficient of the middle term that is, (-10)(4) = -40 (-10) + 4 = -6 so (x - 10)(x + 4) for the second one: 3x^2 + 20x - 7 = 0 , what method have ...
October 24, 2016

Math
make a sketch. split the figure into a rectangle and a right-angled triangle. in the triangle the base will be 21-13 or 8 cm and the hypotenuse is 17 let the height be h h^2 + 8^2 = 17^2 h^2 = 225 h = 15 area = rectangle + triangle = 13(15) cm^2 + (1/2)(8)(15) = 255 cm^2
October 24, 2016

math
to be divisible by 6, it must be divisible by 2 AND 3 8454 is even, so it is divisible by 2 the sum of the digits of 8454 is 21, which is divisible by 3, so 8454 is divisible by 3 (divisibility test for 3: if the sum of the digits of any number is divisible by 3, so is the ...
October 24, 2016

Math
What is C(4,3) ?
October 24, 2016

Math
π is indeed an irrational number , but Don Ho said π = 3.14, which is not true, since 3.14 = 314/100 or 157/50 and that would be a rational number all radicals that are not perfect squares, are also irrational number e.g. √5
October 24, 2016

MATH
You will need brackets in 6/(3-x) = (7-5x)/6 and (3-x)(7-5x) = 36 21 -22x + 5x^2 = 36 5x^2 - 22x - 15 = 0 (x - 5)(5x + 3) = 0 x = 5 or x = -3/5 the common ratio is 6/(3-x) if x =5, common ratio is 6/-2 or -3 if x = -3/5, common ratio is 6/(3 + 3/5) or 5/3
October 24, 2016

maths
I will assume this is an arithmetic sequence. Let's just use our formulas we know d = 2 sum(10) = 93 ---> n = 10, a = ? (10/2)(2a + 9(2)) = 93 5(2a + 18) = 93 10a + 90 = 93 10a = 3 a = .3 check: 10th term = a+9d = .3 + 18 = 18.3 sum(10) = (10/2)(first + last) = 5(.3+18....
October 23, 2016

maths percentage
You appear to have a typo ---- 3205% ????
October 23, 2016

maths need help too hard
4^x+3^x=9^x 4^x+3^x=3^(2x) 4^x = 3^(2x) - 3^x) 4^x = 3^x(3^x - 1 (4/3)^x = 3^x - 1 preliminary check: if x = 1 4+3 = 7 < 9 if x = 2 16 + 9 = 25 < 81 .. if x = 6 4^6 + 3^6 = 4825 < 9^6 for x ≥ 1, the gap between LS and RS is increasing, and RS > LS let's ...
October 23, 2016

Maths
written as a recursive : t(1) = 6 t(n) = t(n-1) + k+1, where k >1 as a function of n, double the terms: 12, 20, 30, 42 ... 12 = 3*4 20 = 4*5 30 = 5*6 42 = 6*7 looks like t(n) = (n+2)(n+3)/2 <--- remember we doubled
October 23, 2016

Mathematics
the equation must look like: y = a(x-2)^2 - 8 and it must pass through (0,0) 0 = a(-2)^2 - 8 8 = 4a a = 2 equation: y = 2(x-2)^2 - 8
October 23, 2016

Math
let's consider midnight as time zero 10:43 - 8:17 = 2:26 So it must have left 2 hours and 26 minutes before midnight, or the bus left town A at 9:34 pm or: we could use international time format let's add 24 hours to 8:17 to get 32:17 and 32:17 - 10:43 = 21:34 which is...
October 23, 2016

Maths
In a rectangle, the two diagonals right-bisect each other. Since they are equal, and we are told the angle between them is 45°, our rectangle must be a square. let the side of the square be x x^2 + x^2 = 6^2 2x^2 = 36 x^2 = 18 x = √18 = 3√2 or appr 4.26 cm The ...
October 23, 2016

math
360 = 2*2*2*3*3*5 = (2^3)(3^2)(5)
October 23, 2016

math
how many 3/8 's do you see? 3/8 x 3/8 x 3/8 = (3/8)^3
October 23, 2016

Algebra
Just concentrate on copper only. let the amount of the 70:30 alloy used be x g then the amount of the 40:60 alloy used is 300 - x .7x + .4(300-x) = .6(300) .7x + 120 - .4x = 180 .3x = 60 x = 200 so 200 g of the 70:30 alloy and 100 g of the 40:60 alloy checking for the zinc: .3...
October 22, 2016

math
x and y are defined in the question, so the cost equation would be cost = 13x + 18y so for b) you know cost = 168, x = 6 168 = 13(6) + 18y 168 = 78 + 18y 90 = 18y y = 90/18 = 5 He bought 6 t-shirts and 5 pairs of jeans
October 22, 2016

PLEASE HELP Math
amount of 1st part: i = .08/12 = .006666.. n = 96 paym = 50 amount = 50( 1.0066..^96 - 1)/.00666.. = $6693.43 amount of 2nd part: i = .10 n = 4 paym = 2000 amount = 2000(1.1^4 - 1)/.1 = $9282.00 total amount = $6693.43 + $9282.00 = $15,975.43 Looks like Colin is not yet ready ...
October 22, 2016

Math
i = .15/12 = .0125 n = 24 payment = 23 PV = 23( 1 - 1.0125^-24)/.0125 = 474.36
October 22, 2016

integrals
The word "power rule" is usually associated with derivatives, but your subject title is "integrals" so what do you want done with it 1/((x^2+4))^2 = (x^2 + 4)^-2 dy/dx = -2(x^2 + 4)^-3 (2x) = -4x/(x^2 + 4)^3 if you want to integrate, it will be a bit harder.
October 22, 2016

math
Of the two choices, only a) and b) have a slope of -6 (-12,5) does not satisfy a) but it does satisfy b) so b)
October 22, 2016

Math
I will assume that the three smaller parts are equal rectangles. Let the width of one of the smaller rectangles is x and its length is y Make a sketch and you should see that our original field is 3x by y and perimeter is 6x + 4y so 6x + 4y = 2400 3x + 2y = 1200 y = (1200 - 3x...
October 22, 2016

Math
cost(d) = 35d + 14.95d + 19(3.40) = 49.95 d + 64.60 where d is the number of days So for 9 days, replace d with 9 and evaluate.
October 22, 2016

Business Mathematics
Just use your formulas "8th term is 18" ---> a + 7d = 18 "11th term is 24 ---> a + 10d = 24 subtract them: 3d = 6 d = 2 in a+7d = 18 ---> a + 14 = 18 , a = 4 now use your sum(n) formula your a = 4 d = 2 n = 13
October 22, 2016

Math, Functions
I disagree with what Christos did it said solve g(t) = 0 , not find g(0) First of all I am sure you meant: g(t) = 1/(t-2) - 1 so if g(t) = 0, 1/(t-2) - 1 = 0 1/(t-2) = 1 t - 2 = 1 t = 2
October 22, 2016

math
let the work to be done be 1 unit rate of first crew = 1/8 job done by first crew in 2 hours = 2(1/8) = 1/4 job left to be done = 1 - 1/4 = 3/4 rate of second crew = 1/10 time needed for 2nd crew to finish = (3/4) / (1/10) = 30/4 hrs or 7.5 hrs
October 22, 2016

Maths
original rectangle: area = 7(4) cm^2 = 28 cm^2 new rectangle: area = (14)(8) cm^2 = 112 cm^2 ratio of new to old = 112 : 28 = 4 : 1 The ratio of the areas of similar figures is proportional to the square of their corresponding sides, that is 2^2 : 1^2 = 4 : 1
October 22, 2016

math
How many seconds are there in 1 hour? multiply that by 24
October 22, 2016

Precalc
let each of the equal sides of the triangle be x let the radius of the circle be r area = (1/2)(x)(x) + πr^2 = x^2/2 + πr^2 we know that if the hypotenuse of the triangle is is h x^2 + x^2 = h^2 2x^2 = h^2 h = x√2 then 2x + √2 x + 2πr = 100 r = (100...
October 21, 2016

Math
correct
October 21, 2016

math
1/3 * -1 1/5 the * symbol is used in this format to stand for multiplication so if you mean (1/3)(-6/5) , then = - 6/15 = -2/5 or -0.4
October 21, 2016

Maths
6^2 + 2^2 + 3^2 = 49 so the direction cosines are (6/7 , 2/7, 3/7) notice that (6/7)^2 + (2/7)^2 + (3/7)^2 = 1
October 21, 2016

Math
I agree
October 21, 2016

Math
Treat the question as if you had two ordered pairs (3,800) and (5,720) slope = (720-800)/(5-3) = - 40 using(3,800) y - 800 = -40(x-3) y = -40x + 920 b) so after 1 year, x = 12 y = -40(12) + 920 = 440 state your conclusion using the proper units
October 21, 2016

Math
Rent it Cheap = 2900 + 50k Thrift car = 3700+48k solve 2900+50k = 3700+48k and use the result to state your conclusion
October 20, 2016

Algebra
2𝑦 + 5 = 1/2(4𝑦 + 8) multiply both sides by 2 4y + 10 = 4y + 8 10 = 8, ahhh, I see your problem, the y's dropped out ok, if your variables drop out, and you end up with a false statement, such as our 10=8, then the equation has no solution. If we end up ...
October 20, 2016

Math
"2n up3" ?? did you mean 2n^3 ? or perhaps (2n)^3 ? clarify please.
October 20, 2016

Math
let the middle number be x then x/5 = 245/x x^2 = 1225 x = ± 35
October 20, 2016

Math
940 = 20 x 47 ---> 47 is prime 420 = 20 x 21 The GCF = 20
October 20, 2016

maths
c) ii) you asked how many study French, but your first data information says that 9 study French Either you meant 9 to be "French only" , or else the question is bogus. Confirm.
October 20, 2016

Algebra
area of the 4 windows = 4(30/12)(48/12) = 40 ft^2 area of floor = 10(40) = 400 ft^2 (where does the ridiculous height of 50 ft come in ?) ratio of window area : floor area = 40:400 = 1:10
October 20, 2016

Math
1st derivative: -sinx 2nd derivative: -cosx 3rd derivative: sinx 4th derivative: cosx 5th derivative: -sinx .. 14th derivative: etc. notice we are in a cyclical loop of 4 results, notice 999 leaves a remainder of 3 when divided by 4, so the result is the same as the 3rd ...
October 20, 2016

Math help please!
done, look at Dan's problem below. Are you switching names?
October 18, 2016

Math Please help
let the number of units be x return = 9x cost = .4(9x) + 50000 at "break-even" point, they are equal 9x = 3.6x + 50000 5.4x = 50000 x = 9259 carry on
October 18, 2016

Algebra
Neither one has an average elevation of -2 Average elevation of Long Beach = (360 + (-7) )/2 = 176.5 units You do the other one in the same way to show the question is bogus
October 18, 2016

Science, Math
Your choices make no sense to me
October 18, 2016

Science Earth
If 10 million years ----> 1 cm 4.6 billion/(10million) = 4.6 x 10^9/(10 x 10^6) = 460 You will need 460 cm or 4.6 metres
October 18, 2016

Maths
346° + 30° = 376° = 360° + 16° = 1 rotation + 16°<----- same as a direction of 16°
October 18, 2016

Geometric progression
apparently three numbers are in a GP then the 3 numbers are: a, ar, and ar^2 "the continued product of three numbes in g.p. is 216" I am guessing you mean: a(ar)(ar^2) = 216 a^3 r^3 = 216 ar = 6 a = 6/r "the sum of their products in pair is 156" a(ar) + a(...
October 18, 2016

Geometric progression
Let the original numbers be a, a+d, and a+2d 3a + 3d = 15 or a+d = 5 ----> d = 5-a after the addition, the three numbers are: a+1, a+d+4, and a+2d+19 they are now in GP, that is .... (a+d+4)/(a+1) = (a+2d+19)/(a+d+4) (a + 5-a + 4)/(a+1) = (a + 10-2a + 19)/(a + 5-a + 4) 9/(a...
October 18, 2016

Algebra2
following up on John's observation, let y = k/x for (5,2) 2 = k/5 k = 10 y = 10/x check for (10,1) is 1 = 10/10, yes check for the last one: (20, 1/2) is 1/2 = 10/20 , yes
October 17, 2016

Math
If 3/8 of the 240 students are boys, then 5/8 will be girls or 15 will be girls. 3/5 of the girls have short, so I will assume that 2/5 will have long hair, assuming none of the girls are bald (2/5)(15) = 6 6 of them have long hair
October 17, 2016

Math
because I can write is a fraction .57 = 57/100
October 17, 2016

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