Sunday

April 20, 2014

April 20, 2014

Total # Posts: 26,034

**algebra 1**

Here is a graph of the situation. http://www.wolframalpha.com/input/?i=plot+y%3D-0.05x+%2B+12+%2C+-40%3Cx%3C40 The way it is stated the equation makes little sense to me. Is x the time relative to Sept 21 ? Is -40<*<40 supposed to mean -40 < x <40 ? that is, are yo...

**algebra 1**

Last night , I had given you a full explanation, set-up and even the solution for this problem, even though it only asked for the two inequations at the beginning of my solution. http://www.jiskha.com/display.cgi?id=1385177236 and you responded with, I am confused. What part d...

**cal**

I think you meant: f(x) = x/(x^2 + 1) (or else why not just reduce it to f(x) = 1/x + 1 ? ) for concave upwards, f ''(x) > 0 f'(x) = (1 - x^2)/(x^2 + 1)^2 using the quotient rule and again f''(x) = 2x(x^2-3)/(x^2+1)^3 so when is f''(x) positive ?...

**math**

Huh ? What question above ?

**Math**

use my favourite stats webpage http://davidmlane.com/hyperstat/z_table.html make sure you click "area from a value" enter 20 as the mean 4 as the sd click on "between" and enter 9.5 and 23 calculate to get 0.769

**algebra 1**

Aren't they supposed to be in-equalities? profit = revenue - expenses = 100x + 5y - 30x - 2y = 70x + 3y but 100x + 5y - 30x - 2y ≥ 400 70x + 3y ≥ 400 also 30x + 2y ≤ 200 15x + y ≤ 100 " Marissa can sell up to 8 framed photographs" --- >...

**math**

jhon: i want to add 34+85% i tryed it and i got 62.9 Reminds me of one of my favourite Bert & Ernie cartoons of years ago: temperature: 29° time : 6:15 ---------------- total: 6 : 44

**cal**

even though both Jai and I had the same answer, which is different from the one you picked ? Where would the 8 even come from ????

**cal**

f(x) = x^2 + x^(1/2) f ' (x) = 2x + (1/2)x^(-1/2) f '' (x) = 2 - (1/4)x^(-3/2) or 2 - 1/(4x√x) explanation: (x^(-3/2) = 1/x^(3/2) = 1/(x^(1/2)^3 = 1/(√x√x√x) = 1/(x√x)

**Math help please**

well, zero out of three is not that great. 1. did you notice 4^0 = 1 4^1 = 4 4^2 = 16 4^3 = 64 and 4^4 = 256 ?? 2. The height of the tree in my backyard "depends" on how long it has been there, so .... 3. suppose we have an area of 20 cm^2 and it stays at 20 if the w...

**math(help)**

1. what is 1/6 + 2/6 2. what is 8/8 - (4/8 + 1/8) 3. what is 7/8 - 5/8 4. what is 11/20 - 9/20

**Math**

Some rational numbers are integers. (all I need is one example) fraction--- 6/2 ineger ---- 2 is 6/2 = 2 ? The circumference of a circle varies directly with its radius f(x) = .08x^3 + .6x + 2.8 - certainly not a quadratic , (I see a cub) - I certainly don't see any variab...

**math**

You posted this before, it made no sense then, and it makes no sense to me now. what does x ≥ -13 , -13 mean ?

**math**

What a lot of extra verbiage to state the simple question: How many place settings can I make from 3 kinds of place mats, and 3 kinds of napkins (she can't use the orange ones, since she has only 3) Since all the setting have to be the same, we just have to find one number...

**Pre-Calc Help!!!**

LS = (tanx - tan(π/4)/(1 + tanx(tan(π/4)) ) = (tanx - 1)/(1 + tanx) = RS I used the identity tan(A-B)= (tanA - tanB)/(1 + tanAtanB) and the fact that tan π/4 = tan 45°= 1

**Math**

your equation says: y = -5 now in the given point (-3,1) is the y value equal to -5 ?

**Geometry**

actually, there is an infinite number of solutions one of the properties of a circle is that a triangle is formed with the diameter as a base and the other point on the circle, you will always have a right angle. so the centre would be (5,3) and the radius would be 2√2 e...

**cal**

some patterns you should just recognize. I know how to differentiate and integrate sin (?), but in both cases the derivative of the "angle" which would be the x from the x^2 has to be considered. Sure enough, the derivative of x^2, which would be 2x , is hanging arou...

**cal**

wouldn't that just be 5 cos(x^2) + c ?

**Geometry**

notice the points given form a horizontal line, so the length of the side must be 7 the x coordinate of the third point must be midway between the two points (simple geometry, look at your sketch) let the third point be P P is (-3/2, y) so the distance from P to (2,3) must be ...

**math(help)**

29/59 = appr .4915.. or about 1/2

**math in focus**

number of girls --- x number of boys --- x+121 number of females -- y number of males ---- 3y number of women = y - x number of men = 3y - x - 121 "5/6 of the males were boys " ---> (5/6)(3y) = x + 121 15y = 6x + 726 6x - 15y = -726 2x - 5y = -242 ---- A "2/3...

**Calculus Help!!!**

notice that one parabola opens up, the other down. their intersection ..... x^2 - c^2 = c^2 - x^2 2x^2 = 2c^2 x^2 = c^2 x = ± c ---- y = 0 in both they intersect at (-c,0) and (c,0) using symmetry area = 2∫(2c^2 - 2x^2) dx from 0 to c = 2(2c^2 x - (2/3)x^3) | from...

**Kelly - Amy - Chrissy Calculus**

Why are you switching names ???? Follow the method I showed you in the other two questions of this type. Did you look at the solutions? Let me know how far you get.

**Algebra 1**

better form .... -2x + y = 2 ---> 2x - y = -2 4/3x+y=19/3 ----> 4x + 3y = 19 1/2x+y=-13/2 ----> x + 2y = -13 9/7x+y=-3/7 ---->9x + 7y = -3 7/9x+y=-10/3 ----> 7x + 9y =-30 can you see what I did? A proper way to write equation in standard form: - no fractions sho...

**Chris - Amy -Calculus Area between curves**

Why are you switching names ?? find the intersection; from the first: x = 3 - 3y into the 2nd: y^2 - (3-3y) = 1 y^2 + 3y - 4 = 0 (y+4)(y-1) = 0 y = -4 or y = 1 in x = 3-3y .... if y = 1, x = 0 ---->(0,1) if y = -4 , x = 15 , ---> (15, -4) Your sketch should look like thi...

**Calculus-Area between curves**

first of all reduce the equation to simplest form: y = 2√x y = 5 y + 2x = 4 Your sketch should look like a "triangle" with one side slightly curved see: http://www.wolframalpha.com/input/?i=plot+y%3D2*sqrt%28x%29+%2C+y%3D5+%2C+y%2B2x%3D4 we need all the interse...

**Algebra 1**

slope = (4-2)/(5-(-1)) = 1/3 pick (5,4) y-4 = (1/3)(x-5) times 3 3y - 12 = x - 5 x - 3y = -7 check: does the point I didn't use satisfy the equation? for (-1,2) LS = -1 - 3(2) = -7 = RS ......... all is good!

**Finance**

amount in 2000 = 2000(1.015)^20 = 2693.71 plus the extra 500 in year 2000 =3193.71 This will earn for 4 years final amount = 3193.71(1.0175)^16 = 4215.47

**algebra**

Trying x = ± 1, ± 5 I get a zero when x = -1 by synthetic division: (x+1)(x^4 + 2x^3 - 4x^2 - 10x - 5) = 0 well, what do you know, x = -1 works again, so (x+1)(x+1)(x^3 + x^2 - 5x - 5) = 0 grouping the last part (x+1)(x+1)( x^2(x+1) - 5(x+1) ) = 0 (x+1)(x+1)(x+1)...

**algebra**

so 50 = -t^3 + 34t^2 - 284t + 490 t^3 - 34t^2 + 284t - 440 = 0 I tried t = ± 1, ± 2 and sure enough when t = 2, I had a solution using synthetic division, (t-2)(t^2 - 32t+ 220) = 0 (t-2)(t-10)(t-22) = 0 t = 2 or t = 10 or t = 22 Since the ride lasted 25 minutes, ...

**cal**

f(x) = x^-2 - 2x - 8 f ' (x) = -2x^-3 - 2 f '' (x) = 6x^-4 extrema: -2/x^3 = 2 x^3 = -1 x = -1, f(-1) = 1 - 2(-1) - 8 = -5 at x = -1, f ''(-1) is > 0, so (-1,-5) is a minimum my answer confirmed by http://www.wolframalpha.com/input/?i=plot++y+%3D+1%2Fx%5...

**check: Algebra 1**

I assumed your constant would have been correct, wrong assumption. go with kuai's solution, but write it as x- 2y = -7

**Algebra 1**

It is considered "poor form" to have the equation in standard form start with a negative x or containing fractions. so the 1st one I would write as x - y = -8 the last one: firs of all it should have been (-1/2)x + y = 23/2 multiply each term by -2 x - 2y = -23

**geometry**

correct

**geometry**

dodecagon --- 12 sides It must be regualar, that is, all sides must be equal and all 12 interior angles are equal. sum = 180(n-2) so each angle = 180(n-2)/n for 12 sides: each angle = 180(12-2)/12 = 150° you do the one with 20sides

**6th grade math**

nope http://www.wolframalpha.com/input/?i=plot+%281%2C5%29%2C+%282%2C5%29%2C+%283%2C5%29%2C+%284%2C5%29 notice all their y values are the same, y = 5 so it is a horizontal line

**math**

Your question makes no sense to me What is $150 ? Is the 8% rate compounded monthly? What is the $12.87 supposed to represent? You did not define m, r and t

**algebra**

Is what answer true or false ?? 8x-2 = -9+7x x = -7

**LOL @ Steve --**

Hilarious Captain: What happen ? Mechanic: Somebody set up us the bomb. Operator: We get signal. Captain: What ! Operator: Main screen turn on. Captain: It’s you !! CATS: How are you gentlemen !! CATS: All your base are belong to us.

**MATH**

Great read: Outliers by Malcolm Gladwell

**College Algebra**

your equation only has one variable. 5x + 3y = 60 3y = -5x + 60 y = (-5/3)x + 20 the y intercept of 20 ( or y = 20) gives you the number of gumballs (y) you can buy for 60 cents if you buy zero mints.

**cal**

f'(x) = 6x^2 - 6x - 12 = 0 for a max/min (critical value) divide by 6 x^2 - x - 2 = 0 (x-2)(x+1) = 0 x = 2 or x = -1 so, yes, x=2 is a critical number, (the other is x = -1) f '' (x) = 12x-6 f(2) = 2(2^3) - 3(2^2) - 12(2) + 18 = -2 f '' (2) = 24-6 > 0 si...

**clarification - math(help)**

Just because one of the numbers is a prime, does not mean the fraction is in lowest terms. e.g. 13/26 = 1/2 21/7 = 3 the numerator and denominator have to be "relatively prime", that is, no whole number exists that divides into both of them

**math(help)**

Why didn't they just ask, " Is 138435 evenly divisible by 3 ? " yes it is. is 38/53 in lowest terms? yes it is, since no whole number divides into both 38 and 53 here is a little-known trick: find a key a b/c on your calculator enter: 38 a b/c 53 = you will g...

**Maths**

I will assume that the building with side BC is on top of the cliff and A is at the bottom of the cliff. step1: tan44= AB/200 AB = 200tan44 so AC = 80 + 200tan44 let angle CPA = Ø tanØ = AC/200 = (80 + 200tan44)/200 tanØ = 1.365 Ø = 53.79°

**cal**

I will assume that you meant f(x) = 2x^(3/2) - 6x^(1/2) (or else we could just divide out the 2's in the first term) f ' (x) = 3x^(1/2) - 3x^(-1/2) f '' (x) = (3/2)x^(-1/2) + (3/2)x^(-3/2) or (3/2)( 1/√x + 1/(x√x) )

**6th grade math**

1. all three are correct 2. "they ate 1/5 of the bag" is not clear Did they eat 1/5 of a full bag, or Did they eat 1/5 of what was in the bag when she arrived?

**Algebra 1**

y+4 = x-2 y = x - 6 ---> usually called the y intercept - slope form or x - y = 6 ---> some texts call this standard form and this x-y - 6 = 0 ---> general form

**Algebra, URGENT!!!**

1. x^2 + (x+6)^2 = 8^2 x^2 + x^2 + 12x + 36 - 64 = 0 2x^2 + 12x - 28=0 x^2 + 6x - 14 = 0 x^2 + 6x = 14 , completing the square .... x^2 + 6x + 9 = 14+9 (x+3)^2 = 23 x+3 = ± √23 x = -3 ± √23 but x has to be positive so x = √23 - 3 so one leg is &...

**College Algebra**

A = 25000 e^(.06(5)) A = 25000 e^.3

**home school**

let the numbers be x and y x+y = 42 ---> y = 42-x xy = 185 --->x(42-x) = 185 42x - x^2 - 185 = 0 x^2 - 42x + 185 = 0 (x-37)(x - 5) 0 x = 37 or x = 5 then y = 42-37 or y = 42-5 y = 5 or y = 37 (symmetric solution) the two numbers are 5 and 37

**Algebra NEED HELP ASAP!!!!!!**

T = 4h + 72 , 0 < h < 12, where h is the number of hours at noon , h = 6 T = 72 + 4(6) = 96

**cal**

did you mean it the way you typed it, or did you mean f(x) = √(x+2) ? I will assume f(x) = √(x + 2) judging by the values of the interval first take the definite integral of the function = ∫(x+2)^(1/2) dx from 1 to 7 = (2/3)(x+2)^(3/2) | from 1 to 7 = (2/3)9^...

**Math Properites**

= (3.4)(3.8)(10^5)(10^-9) = 12.92(10^-4) = 12.92/10000 = .001292

**TRIANGLE SIMILARITIES RATIOS AND PROPORTIONS**

The key to this question is to realize that all the right -angled triangles are similar, and have the ratio of 3:4:5 in the length of their sides. Mark the two angles in triangle BCD with o and x ( you should be able to see that since XD | BC , so you can mark XDC as o and DCX...

**Pre-Calculus**

did you notice that f(x) = (x-9)(x-2)/(x-9) ?? = x-2, x ≠ 9 So for all values of x except x=9 the given function reduces to f(x) = x-2 which is a straight line. when x = 9, the original gives you 0/0 which is indeterminate, while the reduced function gives you (9,7) So t...

**algebra 2**

Prob(cheese, then turkey) = (6/15)(5/14)= = 30/210 = 1/7

**MATHS**

all multiples of 7 are $1 7, 14, 21 ------- $3.00 all multiples of 6 are .50 6,12,18,24,------- 4(.50) = $2.00 all multiples of 5 are .20 5,10,15,20 ---- 4(.20) = $.80 all multiples of 4 are .10 4,8,12,16,20,24 but the 12, 20 and 24 have been changed, so only the 4,8, and 16 c...

**Advanced Funtions**

if either x or y , or both = 0

**Advanced Functions**

They were the most obvious ones.

**Advanced Functions**

sin 60° = √3/2 cos 30° = √3/2 sin 120° = √3/2

**PRECALCULUS**

solve both as quadratics that factor 1. 2cos^2 x - 5cosx + 2 = 0 (2cosx - 1)(cosx - 2) = 0 cosx = 1/2 or cosx = 2 but cosx = 2 is not possible, since -1 ≤ cosx ≤ +1 for cosx = 1/2, since it is positive, x could be in I or IV x = 60° or x = 360-60 = 300° 2. ...

**Advanced Functions**

if cosx = 5/13, (recognize the 5,12,13 triangle ?) sinx = 12/13 tanx = 12/5 if cosy = -5/13 and y is in III siny = -12/13 tany = 12/5 2sinx+2siny+2cosx-2tanx+tany+2cosy = 2(12/13) + 2(-12/13) + 2(5/13) -2(12/5) + (12/5) + 2(-5/13) = - 12/5 or -2.4

**Trig - Law of sines and cosines**

I started with AB, the vertical diagonal of the square. I then drew square ALMN At M, I drew the base BC of the equilateral triangle perpendicular to AM, letting BM = MC = 2 Joi AB and AC for the triangle. Let the intersection of ML and AB be P, and the intersection of MN and ...

**algebra 2**

What is your question? What does "3/4 Six lots" mean?

**algebra**

BTW, Steve answered you yesterday when you posted it then. Did you not look at his answer?

**algebra**

prob(rain on Sat and Sun) = (10/100(30/100) = (1/10)(3/10) = 3/100 or 3%

**Algebra**

multiply each term by ab, the LCD bx - ab = ay y = (bx - ab)/a or just multiply both sides by b bx/a - b = y , which is the same as my first result

**algebra**

let the amount invested at 11% be x so .11x + .12(x+4000) = 940 .11x + .12x + 480 = 940 .23x = 460 x = 2000 So originally you had $2000 in the 11% account and $6000 in the 12% account at the end you had 2220 and 6720 respectively check: 2220+6720-8000 = 940

**Geometry (math)**

True No need to draw a figure, just look at the screen on your computer. let s be the top of the screen let q be perpendicular of your screen, how about the left side? let p be the bottom of your screen Is the top of your computer screen not parallel to its bottom?

**Math**

geesh, forgot to put D) in front D) which means that for every increase of 1800 feet, the temperature would decrease by 1° or for every decrease of 1800 ft , the temperature would rise by 1° F B) so how did Tessa get +.9/-.5 ? look at the bottom number of -.5. where di...

**Math**

clearly Gemma used the first two pairs, just check the calculations. B) which difference in the first elements would give you -.5 ?? c) no matter which pair you take you get a slope of -1.8 or -1.8 : 1 or -1800 ft : 1° F which means that for every increase of 1800 feet, th...

**math**

prob(yellow) = x/(20+x) but we know this is 1/6 x/(20+x) = 1/6 6x = 20+x x = 4 so there are 24 balls, of which 9 are blue so Prob(blue) = 9/24 = 3/8

**Math questions**

think of 8 as the slope and (12,240) as an ordered pair for this relation y = -8x + c at (12,240) 240 = -8(12) + c c = 336 y = -8x + 336 so when x = 0, y = 336 Where was he when x = 0 ???? at ground, y = 0 solve 0 = -8x+240 8x = 240 etc ....

**algebra**

What do you think? I don't see your choice of answer for any of them.

**Pre-Calculus**

since the line is perpendicular, their slopes are negative reciprocals of each other, that means, they must be OPPOSITE in sign so first slope = -3/2 2nd slope = +2/3 y-2 = (2/3)(x-4) 3y-6 = 2x-8 3y = 2x - 2 y = (2/3)x - 2/3

**Math Help**

#2 is correct #3 solving your 2 equations: 1st times 2: 8b+6n=47 2nd times 3: 15b+6n=64.5 subtract them: 7b = 17.5 b = 2.5 sub back in ----> n = 4.5 necklace costs $4.50 and bracelet costs $2.50 so buying just one each = $7.00

**Math Help**

first one: your equation: B = 22 +11.5w , where B is the balance, and w is the number of weeks or y = 22+11.5x to make it fit your x = 8 your friend: y = 218-13x if x = 8, you will have 22+11.5(8) = 114 your friend has 218-13(8) = 114 What do you think? Give the other two a sh...

**Math**

number of small posters x number of large posters y cost of small posters 240/48 = 5 cost of larger posters 240/30 = 8 5x+8y=240 to graph it, I would use intercepts let x = 0, y = 30 --->(0,30) let y = 0 , x = 48 ---> (48,0) slope = (0-30)/(48-0) = -5/8 For each reductio...

**Geometry**

Use the results of the ratio properties I gave you in your previous post

**geometry**

For the question to be "workable", AF is probably the median, with F on BC remember the centroid cuts the median in the ratio of 2:1, or AG:GF = 2:1 then FG:AF = 1:3 (x+8)/(9x-6) = 1/3 9x - 6 = 3x + 24 6x = 30 x = 5

**My fuzzy thinking - math**

Forget my previous post, r could be 1.5 my program line 60 should say: 60 if (b*c*d)^2 = (a*b*c^2*d*e) then print a;b;c;d;e and I got 64 96 144 216 324 80 120 180 270 405 96 144 216 324 486

**math**

I think I missed the obvious Since a,b,c,d,e are integers in GS, the smallest value of r is 2 a - b - c - d - e 51 102 204 408 816 52 104 ... 53 .... infinite number of choices for a so... still a silly question

**For Steve - math**

Crazy question. Agree with you, there has to be more As it stands: b/a = c/b and c/b = d/c and d/c = e/d b^2 = ac , c^2 = bd , d^2 = ed then b^2 c^2 d^2 = abcde I then ran this "primitive" BASIC program 10 for a = 50 to 100 20 for b = 51 to 100 30 for c = 52 to 100 4...

**Calculus**

Write it as f(x) = 7x^-2 - 6x^-6 F(x)= -7x^-1 + (6/5)x^-5 + c F(2) = -7/2 + (6/5)/2^5 + c = ......

**Calculus**

let the side of the square be x let the side of the triangle be y 4x + 3y = 40 x = (40-3y)/4 height of triangle from the 30-60-90 triangle ratio = √3/2 y area of triangle = (1/2)(y)(√3/2 y) = (√3/4)y^2 area of square = [(40-3y)/4]^2 = (1600 - 240y + 9y^2)/16 ...

**TO ANY MATH HELPERS**

1. from the 1st equation: x = 3y+1 into the 2nd: 3(3y+1) - y +1 = 0 9y + 3 - y +1 = 0 8y = -4 y = -1/2 sub into 2nd: 3x - (-1/2) + 1 = 0 3x = -3/2 x = -1/2 Do #2 the same way from the 2nd: y = 2x+4 etc (Just stating the answers is not acceptable and serves no purpose)

**math and physics**

asks for login and password

**math**

just did it http://www.jiskha.com/display.cgi?id=1384818273

**math**

36 = 1x36 = 2x18 = 3x12 = 4x9 = 6x6 = 9x4 = ....

**Math**

1 more than half of x should be x/2 + 1

**math**

To add/subtract something, they must be in the same units e.g 5 apples + 8 oranges = 13 appleoranges? so 2 hrs, 45 minutes = 2 + 45/60 = 2.75 hrs 3hrs, 57 minutes = 3 + 57/60 = 3.95 hrs now you can add them: 2.75+3.95 = 6.7 hrs = 6 hrs + (7/10)(60) minutes = 6 hrs, 42 minutes ...

**math**

As an after-thought ..... Tn = T(n-1) + 4 , T1 = -40 , n > 1 In the recursive notation, the initial value has to be included or else you can't begin your sequence.

**Precalculus**

tanØ secØ = tanØ tanØ secØ - tanØ = 0 tanØ(secØ - 1) = 0 tanØ = 0 or secØ = 1 if tanØ = 0 Ø = 0, 180°, 360° ... , 180k° , where k is an integer if secØ - 1 then cosØ =...

**Precalculus**

sec(Ø + 81) = 2 cos(Ø + 81) = 1/2 I know cos 60° = 1/2 so Ø+81 = 60 or Ø+81 = 300° Ø = 60-81 = -21° or Ø = 219° now the period of cos(Ø+81) = 360° so adding 360 will give me another answer so Ø = -21 +...

**math**

lots of missing information What was the rate of interest? Did he make any monthly payments? Did he make not payments except the one at the end of 31 months?

**Math-Algebra**

A direct square variation is a quadratic Given any 3 points , I can find that quadratic, but we can't "force" a fourth point on it. e.g A = 20.115r^2 - 101.835r + 135.78 produces the first 3 points , but not the last one

**Math-Algebra**

What is the topic for this question? Are you learning about "curve fitting" ?

**Math-Algebra**

Not enough data to see a pattern http://www.wolframalpha.com/input/?i=plot+%282%2C12.57%29%2C+%283%2C11.31%29+%2C+%284%2C50.28%29%2C+%285%2C78.56%29

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