Sunday
July 5, 2015

Posts by Reiny


Total # Posts: 30,330

Math
for the mean, add them up and divide by 5 for the sd: take the difference between each of the data values and the mean and square that result repeat for all 5 of them add them up, divide by either 5 or 4 depending on the definition of sd you are using, take the square root. ...
May 6, 2015

Algebra
term4 = a+3d = 15 term10= a+9d = 39 subtract them 6d = 24 d = 4 in a+3d = 15 a + 12 = 15 a = 3 term40 = a+39d = ... sum40 = (40/2)(2a + 39d) = ...
May 6, 2015

Trig
if sinA = 12/13, and since the since is + A must be in II using our standard 5-12-13 triangle, cosA = -5/13 if sinB = -7/25, to state -90 ≤ B ≤ 90 is ambiguous, since you could be on the right or the left of the y-axis I will assume B is in III , (could be in IV) ...
May 6, 2015

math
cost of 6 vans at the end of 4 yrs = 148800 i = .03 n = 4(4) = 16 P(1.03)^16 = 148800 solve for P
May 6, 2015

Math Help
the parabola is vertical, and opens downwards standard form x^2 = 4py but vertex is (-1,2) (x+1)^2 = 4p(y-2) but p = -2 (x+1)^2 = -8(y-2) (x+1)^2 = -8y + 16 8y = -(x+1)^2 + 16 y = (-1/8)(x+1)^2 - 2 for the 2nd , use y^2 = 4px and follow the above steps
May 6, 2015

Calculus
y ' = sec^2 ((1 - x)^(1/2) ) (1/2)(1-x)^(-1/2) (-1) clean it up to whatever level you need it simplified.
May 6, 2015

Calc 1
f ''(x) = 6+cosx f '(x) = 6x + sinx + c f (x) = 3x^2 - cosx + cx + k f(0) = 1 0 - cos 0 + 0 + k = 1 -1 +k= 1 k = 2 so f(x) = 3x^2 - cosx + cx + 2 f(7π/2) = 0 3(7π/2)^2 - cos(7π/2) + (7π/2)c +2 = 0 solve for c, plug into the f(x) equation and you...
May 6, 2015

Math/algebra
ok, then you know f + t = 70 or t = 70-f recall that the equation said: 5f + 10t = 595, which we reduced to f + 2t = 119 replace t with 70-f f + 2(70-f) = 119 f + 140 - 2f = 119 -f = -21 f = 21 so she has 21 fives. Can you take it from there ?
May 5, 2015

Math
several ways: if x = (2 ± √5)/3 then the factors are (x - (2 +√5)/3) and (x - (2 - √5)/3) then (x - (2 +√5)/3)(x - (2 - √5)/3) = 0 ( x - 2/3 - √5/3)(x - 2/3 + √5/3) = 0 x^2 - 2x/3 + x(√5/3) - 2x/3 + 4/9 - 2√5/9 - x&#...
May 5, 2015

Math
e.g. in 5x^2 + 7x - 18 a=5 b=7 c=-18 Your question is poorly worded a stands for the coefficient of the x^2 term b stands for the coefficient of the x term c stand for the constant
May 5, 2015

math
let the total be x A got (3/7)x = 3x/7 B got (2/3)(3x/7) = 6x/21 = 2x/7 C got 3x/7 - 49 3x/7 + 2x/7+ 3x/7 - 49 = x times 7 3x + 2x + 3x - 343 = 7x x = 343 A has 147 B has 98 C has 98 ratio of B:C = 1:1
May 5, 2015

Math
you are saying there are 3 points on the graph, but the table shows 4 points. mmmhhh? anyway: take the slope of all possible pair of points, what do you get ?
May 5, 2015

Algebra
f stands for the number of $5 bills, so by saying f = 5, you are saying there are five $5 bills. It does not say that anywhere ---------- let f be the number of fives let t be the number of tens so the VALUE of our fives = 5f and the VALUE of our tens = 10t 5f + 10t = 595 ...
May 5, 2015

Math - 7th grade
Good job, I agree with all your answers
May 5, 2015

Calc 1
let the point of contact be (x,y) or (x, -6sinx) Then for a tangent, slope = m = (-6sinx - 0)/(x-0) = -6sinx/x m = (-6sinx - 0)/(x-0) = -6sinx/x dm/dx = (x(-6cosx - (-6sinx))/x^2 , by quotient rule = 0 for a max/min -6xcosx + 6sinx = 0 xcosx - sinx = 0 xcosx = sinx x = sinx/...
May 5, 2015

Math
You are using the word "combinations" so it would be C(5,3) or 10 of them e.g. suppose you have A, B, C, D, E kind of trees ABC ABD ABE BCD BCE CDE ADE ACE BDE ACD
May 5, 2015

math
To form a triangle, the sum of any two sides must be greater than the remaining third side checking for a) is 17+13> 2 ? Yes is 17+2 > 13 ? Yes is 13+2 > 17 ? NO So 17,13,2 cannot form a triangle Repeat for the others.
May 5, 2015

Algebra Readiness
actually the correct table is C e.g. look at the first one x = -5 y = -5 - 6 = -11 try the others.
May 5, 2015

math
So the angle between them is 72° They both travel for 2 hours, so the 1st went 30 km, and the 2nd went 4 km This is just a cosine law question .... x^2 = 30^2 + 4^2 - 2(4)(30)cos72 = 841.83.. x = appr 29.01 km or, using the fact that the 2nd boat was directly north of the ...
May 5, 2015

Math
That would only be true if the height is equal to the radius
May 5, 2015

Algebra (Slope)
parallel lines have equal slopes, so slope = (6-4)/(2-3) = -2
May 5, 2015

Maths
I did this for you Always check back before reposting the same question.
May 5, 2015

Analytic Geometry
let the new point be (x,y) I will assume you mean XZ = 4XY by simple ratio: for the x's (x+1)/(4+1) = 4/1 x+1 = 20 x = 19 for the y's (y-2)/(11-2) = 4/1 y-2 = 36 y = 38 Z is (19,38) check: XY = √(5^2 + 9^2) = √106 XZ = √(20^2 + 36^2) = √1696 = 4...
May 5, 2015

algebra
speed of freigh --- x speed of passenger ---- x+6 time for passenger to go 330 miles = 330/(x+6) hrs time for freight train to go 300 miles = 300/x hrs but the times are the same 330/(x+6) = 300/x 330x = 300x + 1800 30x = 1800 x = 60 state the conclusion
May 5, 2015

Geometry
By definition of "obtuse", one of the angles must be greater than 90 So if all 3 angles would be obtuse, their sum would be greater than 270° But we know that the total sum of all 3 angles = 180° So, silly conclusion. As a matter of fact , a triangle can have...
May 5, 2015

math
nice problem: b) the easiest, just sub in (5,5) to show it works a) since y = 7x, sub the y into the circle equation x^2 + (7x)^2 = 50 x^2 + 49x^2 = 50 x^1 = 1 x = ± 1 if x=1 , y = 7 , call that A(1,7) if x = -1 , y = -7 , call that B(-1, -7) c) slope AC = (5-7)/(5-1...
May 5, 2015

Maths Problem
let the side of the larger square be x let the side of the smaller square be y 1. x^2 + y^2 = 65 2. y > 1/2x 2y > x initial thought: 65 must be sum of 2 squares, 8 and 1 immediately come to mind but 2(1) is not greater than 8 how about 7 and 4 ? is 7^2 + 4^2 = 65 ? YES ...
May 5, 2015

geometry
Which sides are parallel ?
May 5, 2015

math
i = .0825 n = 6 amount = 27000(1.0825)^6 = .....
May 5, 2015

math
number of total choices = 3 x 3 x 2 = 18 number of choices with yellow or green tofu and tea = 3 x 2 x 1 = 6 prob(stated event) = 6/18 = 1/3
May 5, 2015

college precalculus
i = .06/12 =.005 n = 8(12) = 96 P(1.005)^96 = 2000 solve for P
May 5, 2015

trigonometry
Clive probably meant: (1+sin 2A)/cos 2A = (cosA + sinA)/(cosA - sinA) LS = (sin^2 A + cos^2 A + 2sinAcosA)/(cos^2 A - sin^2 A) = (cosA + sinA)/( difference of squares) = ... I am sure you can take it from there
May 5, 2015

Algebra
original: 10 cm by 20 cm after cutting x cm at the corners new length = 20 - 2x new width = 10 - 2x height = x volume = x(10-2x)(20-2x) , 0 < x < 10
May 4, 2015

math
B worked for all of them when I tried it.
May 4, 2015

math
I would try subbing in the points e.g. (0,5) works in A,B, and D only (1,4) works in B try if the others work in B well ???
May 4, 2015

math
If it even works, the largest number must be the hpotenuse, so e.g. R is 26^2 + 20^2 = 46^2 ? test the others.
May 4, 2015

math
height/30 = sin60 height = 30sin60 = ....
May 4, 2015

math
2 fracture each third ?? I have no idea what that means.
May 4, 2015

Math
1. f(x) = x^2 - 3x + 2 for f(-2), put in -2 wherever you saw an x f(-2) = (-2)^2 - 3(-2) + 2 = 4 + 6 + 2 = 12 you are correct 2. correct again.
May 4, 2015

math 0312
speed in still water ---- x rate upstream = x-9 , where x is clearly > 9 rate downstream = x+9 17/(x+9) + 17/(x-9) = 13 times (x+)(x=9) or x^2 - 81 17(x-9) + 17(x+9) = 13(x^2 - 81) 17x - 153 + 17x + 153 = 13x^2 - 1053 13x^2 - 34x - 1053 = 0 x = (34 ± √55912)/26...
May 4, 2015

Math 222
is that g(x) = √x - 1 or g(x) = √(x-1) ? make a table of values, pick some x's , find the y's and plot the points
May 4, 2015

Math
A. for Carmen to run 3 times, Susan runs 4 times around the track for Carmen to run 1 times, Susan runs 4/3 around for Carmen to run 12 times, Susan runs 12(4/3) or 16 times around the track (notice that this is a straight ratio thing)
May 4, 2015

Further mathemactics
tan^2 Ø - sin^2 Ø = sin^4 Ø sec^2 Ø LS = sin^2 Ø/cos^2 Ø - sin^2 Ø = (sin^2 Ø - sin^2 Ø cos^2 Ø)/cos^2 Ø , using a common denominator. = (sin^2 Ø - sin^2 Ø(1 - sin^2 Ø)/cos^2 &...
May 4, 2015

trig
I assume you are solving this equation. btw, sec by itself is meaningless, since it is an operator, thus it needs an argument that's like saying 3 + √ = x anyway.... -2sec x = 3 sec x = -3/2 cosx = -2/3 the cosine is negative in quads II and III using my calculator ...
May 4, 2015

math functions
All three are correct #3 is correct assuming you are starting with n = 1
May 4, 2015

Math
Very simple LS = sin^2 x - cos^2 x = sin^2x - (1-sin^2 x) = 2sin^2 x - 1 = RS
May 3, 2015

math
Angles do not have area.
May 3, 2015

trigonometry
Did you not read my post? I told you how to do it.
May 3, 2015

trigonometry
let's just tackle the LS LS = sin(A+B)*sin(A-B) = (sinAcosB + cosAsinB)(sinAcosB - cosAsinB) = sin^2 Acos^2B - cos^2Asin^2B , the difference of squares pattern = (1 - cos^2A)(cos^2B) - cos^2A(1-cos^2B) = cos^2B - cos^2Acos^2b - cos^2A + cos^2Acos^2B = cos^2B - cos^2A = RS ...
May 3, 2015

Math
done look back when you posted it earlier
May 2, 2015

trigonometry
one rotation is 2π so -31π/6 ÷ 2π = -5 - π/6 so we have 5 clockwise rotations and another clockwise of π/6 (remember in trig, counterclockwise is positive and clockwise is negative) or consider the rotations in degrees 31π/6 radians = 930&...
May 2, 2015

trigonometry
Since arctan and tan are inverse operations, then logically arctan(tan(-31π/6)) = -31π/6 however .... since it probably wants the angle closest to the origin, and since tan(-31π/6) = tan(-π/6) arctan(tan(-31π/6) = arctan(tan(-π/6) = -π/6
May 2, 2015

Math - Trigonometry
Ls = 1/cosx - cos^2 x/cosx = (1-cos^2 x)/cox = sin^2 x/cosx = sinx sinx/cox = sinx tanx = RS How can you change 1/cosx - cosx to 1/cosx - cosx/cosx ?? you can't just toss in an extra cosx at the bottom that last term of cosx/cosx would reduce to 1
May 2, 2015

Math - Trigonometry
I have helped you with two of these now. I think it is time for you to try them. Hint: on the LS, find a common denominator and add the two terms Show me your steps and I will help you from there.
May 2, 2015

Math - Trigonometry
This one's really easy ... RS = sin^2 x - cos^2 x = sin^2 x - (1 - sin^2 x) = 2sin^2 x - 1 = LS
May 2, 2015

Math - Trigonometry
LS = 1/sinx + 1/cosx = (cosx + sinx)/(sinxcosx) = (cosx + sinx)(1/sinx)(1/cosx) = (cosx+ sinx)(cscx)(sec) = RS
May 2, 2015

Calc 1
Wasn't your tangent line supposed to pass through the origin?
May 2, 2015

algebra
well, let's just take the slope using the 2 given points slope = (y-2)/(3-1) = (y-2)/2 but we are told that the slope is 2 , so (y-2)/2 = 2 y-2 = 4 y = 6
May 2, 2015

algebra
what is (1/2)(1/2)(1/2) ?
May 2, 2015

Math Calc
You will need the vertex of this parabola I don't know what method you learned , so I will use the simplest way not using Calculus for y = ax^2 + bx + c, the x of the vertex is -b/(2a) so for yours, t = -112/-32 = 3.5 sub that back in to get the maximum height. when it ...
May 1, 2015

math
What is the question? Is this supposed to be an equation looking like 3x^2 - 27x^2 + 60x = 0 ?
May 1, 2015

Math
yes, you got it. it would be x = nπ/2, where n is an integer.
May 1, 2015

Math
since csc Ø = 1/sinØ csc (2x) has asymptotes when sin(2x) = 0 (the amplitude won't matter) sin(2x = 0 then 2x = 0 , ±π, ±2π , ±3π .... x = 0 , ±π/2, ±π, ±3π/2 ... http://www.wolframalpha....
May 1, 2015

Calculus
just notice that 0 < a < 4, so our answers would be the two shown in my solution a = 1.11415714 and a = 2.772605
May 1, 2015

Calculus
no, you were right the first time if y = x + cos(ax) , then dy/dx = 1 - asin(ax) so for a max, asin(ax) = 1 but we are told that x=1 a sin a = 1 sin a = 1/a very hard equation to solve, if you have a good calculator, set it to radians and start trying some values. clearly a &#...
May 1, 2015

math
Let's see how many cubes we can lay along the length, 4.5 ÷ .25 = 18 and along the width, 5 ÷ .25 = 20 and how high can we stock them? 3.75 ÷ .25 = 15 So there would be 18 x 20 x 15 of them or 5400 (and you spent 3 hours on this? not possible!) another...
April 30, 2015

Math 12
A four-of-a-kind is four cards showing the same number plus any other card. If we order the 5-card hand with the four-of-a-kind first, we have C(13,1) choices for the number showing on the first four cards. Since we will have all four suits, we have only C(4,4) = 1 way to ...
April 30, 2015

Math Check
No Prob(first is white) = 4/14 = 2/7 now there are only 13 socks left, so prob(2nd is blue) = 8/13 prob(1st white, then blue) = (2/7)(8/13) = 16/91
April 30, 2015

math homework
that's better, that would simply be 4 x 5 x 2 or 40 ways
April 30, 2015

math homework
This question makes no sense. You say that there are "about" 5 different Star Wars issus, "about" 5 ..... and then you ask for "exactly" how many .... Please clarify.
April 30, 2015

math
Betty ? Kyle ? , please stick to one name No, how can it be simply 40 when the first answer was 59280 ?? You are just guessing and hope that I will give you the solution. Look at my solution for the first one, and tell me why my second multiplier is only 39 instead of 40 and ...
April 30, 2015

math
yes, the first one. How would you do the second one ? How would the solution change ?
April 30, 2015

math
yes, remember there were actually two questions. Which of the two did we answer, and how would you do the other one?
April 30, 2015

math
so there are 40 numbers to pick from. first choice -- 40 2nd choice -- 39 3rd choice -- 38 what is 40*39*38 ?
April 30, 2015

Math
surely you have those in your text or notes. first one: term(n) = a + (n-1)d and you know both a and d term(n) = 4 + (n-1)(8) = 4 + 8n - 8 = 8n - 4 for the second, go to your text, find the formula for term(n) of a GS , and plug in your given values
April 30, 2015

ALGEBRA
part at 4% --- x part at 5% --- 7500-x .04x + .05(7500-x) = 325 after you multiply each term by 100 to get rid of the decimals this is an easy equation to solve. Go for it.
April 30, 2015

ALGEBRA
prob(repair) = 3/100 expected cost = (3/100)($39) = $1.17 cost of agreement = $9.00 so profit per agreement = 7.83 Percentage of profit = 7.83/9 = .87 or 87% (not bad, that is why I never buy these agreements) another way to look at it. Suppose 100 people bought the agreement ...
April 30, 2015

math
First make a sketch, here is Wolfram's version http://www.wolframalpha.com/input/?i=y+%3D+cosx+%2B+1%2Fcosx+for+-%CF%80+to+%2B%CF%80 The vertical lines are asymptotes, and thus will not yield any values. You can see that the min value is appr 2 Here is a larger picture, ...
April 30, 2015

math
1 + 4x + 4x^2 - 16x^4.. ,1 + 2x - 8x^3 - 16x^4.., 16x^4 + 4x^2 + 1 is there a significance to the .. at the end of the first term? if not, then 1 + 4x + 4x^2 - 16x^4 = (1+4x) + 4x^2(1 - 4x^2) = (1 + 4x) + 4x^2(1 - 2x)(1 + 2x) 1 + 2x - 8x^3 - 16x^4 = (1+2x) - 8x^3(1 + 2x^2) 16x...
April 30, 2015

Math
every pair of same factors must be a perfect square and any integer base raised to an even exponent must be a perfect square, so all factors are perfect square except 7^15 which is 7^14 x 7 7^14 is a perfect square, but if I multiply that by 7 it no longer is. we could write ...
April 29, 2015

Please help -_-
Sadie, there was only about 1 hour between the time you first posted this and your second posting. Have some patience, we are volunteers and don't sit here all the time just waiting for questions. In my case I might come here a few times a day, if I see questions ...
April 29, 2015

Calculus-limits
since the power of the numerator is one degree higher than that of the denominator we get y = (9x-x^2-7x^4)/(x^3+12x) = -7x + ?? so as x gets bigger, y gets bigger, so the limit is undefined, (approaches negative infinity, or we can say the limit does not exist
April 29, 2015

easy math
done, always check back before reposting
April 29, 2015

Math
Assuming he picks one topping number = 2 x 16 x 2 = 64
April 29, 2015

mathssss
I will assume you mean: (2c+5)/-5 * (2c+5)/-5 + (4c-2)/5 * (4c-2)/5 = 20 major difference from what you typed, those brackets are critical (4c^2 + 20c + 25)/25 + (16c^2 - 16c + 4)/25 = 20 20c^2 + 4c + 29 = 500 20c^2 + 4c - 471 = 0 solve using the formula
April 29, 2015

math
lw = 60 ---> l = 60/w 2l + 2w = 38 ---> l + w = 19 60/w + w = 19 times w 60 + w^2 = 19w w^2 - 19w + 60 = 0 (w-15)(w-4) = 0 w = 15 or w = 4 , then l = 4 or l = 15 the length is 15 and the width is 4
April 29, 2015

Algebra
always check back before reposting http://www.jiskha.com/display.cgi?id=1430287921
April 29, 2015

Calculus
For any point (a,b) |12a - 9b - 5| /√(144+81) = 2 12a - 9b - 5 = 30 12a - 9b = 35 Now test which ordered pair satisfies this linear equation.
April 29, 2015

algebra 2
no matter what the function f(x) ---> f(x-5) results in a horizontal translation of 5 units to the right look at the graph http://www.wolframalpha.com/input/?i=plot+y+%3D+log%28x%29+%2C+y+%3D+log%28x-5%29+for+0%3C+x%3C30
April 29, 2015

math
arc length of a circle = rØ, where Ø is in radians 5Ø = 10 Ø = 2 radians or appr 114.59°
April 29, 2015

Math
looks like experimental , and the results don't match the theoretical or mathematical probability When rolling a die, the real prob(5) = 1/6
April 29, 2015

Analytic Geometry
given: 4x+3y - 10 = 0 a) easiest way: since the new line is parallel it must look like 4x+3y + c = 0 using your distance formula from a point to a line |4(2) + 3(-1) + c|/√(4^2 + 3^2) = 3 8 - 3 + c = 15 c = 10 4x + 3y + 10 = 0 or -8 + 3 - c = 15 -c = 20 c = -20 4x + 3y...
April 29, 2015

Math
Wasn't there an "experiment" of rolling the dice 160 times? And it came up "2" 39 times So the experimental prob must be 39/160 The theoretical probability is the actual mathematics one, so the "2" is one of the 6 sides, so the experimental ...
April 29, 2015

ALGEBRA
distance = √( (4-(-2))^2 + (-5-3)^2 ) = √(36 + 64) = √100 = 10
April 29, 2015

Algebra
25000(.8)^n = 5000 .8^n = .2 take log of both sides , and using log rules n log.8 = log.2 n = log .2/log .8 = appr 7.2 years
April 29, 2015

Algebra
Choc chip -- 12 oatmeal ---- 12 no-bake ---- 12 peanut butter --12 gingerbread ---12 Sample space = C(60,6) selections of six gingerbread from 12 = C(12,6) prob = C(12,6)/(C(60,6) = .000018456
April 28, 2015

Math
Did you check if the slope between any two points is always the same ? Hint: the point (0,0) is a good point to check in the given equations. Which equation does it satisfy ?
April 28, 2015

Math
I suggest you make a table of sums for 6 rows and 6 columns from the numbers from 1 to 6 Fill in the sums, e.g. the first row and last row would be 2 3 4 5 6 7 .... 7 8 9 10 11 12 count up all the odd ones, obviously 18 of them Remember 2 is a prime number so it must be ...
April 28, 2015

Math
In the first one I think Bob forgot about the other 5 cards that have to be drawn I am going to do these by using combinations P(exactly 2 wild, 5 non-wild) = ( C(8,2) x C(100,5) / C(108,7) = .0756 or using bob's method P(exactly 2 wild, 5 non-wild = 8/108 * 7/107 * 100/...
April 28, 2015

math
make a sketch and let our point needed be (x,y) for the x: (x-(-5))/(6-x) = 2/3 3x + 15 = 12-2x 5x = -3 x = -3/5 for the y: (y+4)/(-2-y) = 2/3 3y + 12 = -4-2y 5y = -16 y = -16/5 your point is (-3/5 , -16/5) or, using vectors (x,y) = (3/5)(-5,-4) + (2/5)(6,-2) = (-3 , -12/5...
April 28, 2015

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