Thursday

July 30, 2015

July 30, 2015

Total # Posts: 30,497

**Pre-Algebra**

1. how did you get 24 ? f(x) = x^2 - 3x + 2 f(-2) = (-2)^2 - 3(-2) + 2 = 4 + 6 + 2 = 12 2. E = 12m 3. correct 4. y = 1.15 + .95(x-1)
*May 12, 2015*

**math**

If you plot the points you will get a rectangle of length 6 and height of 4 so the perimeter is 12 + 8 or 20 units take over
*May 12, 2015*

**Math**

recall the difference of squares: a^2 - b^2 = (a+b)(a-b) this has the same pattern (x+y)^2-(x-y)^2 = (x+y + x-y)(x+y - (x-y)) = 2x(2y) = 4xy or you could just expand the original ... (x+y)^2-(x-y)^2 = x^2 + 2xy + y^2 - (x^2 - 2xy + y^2) = 4xy
*May 12, 2015*

**Trig Identities**

good start LS = sinx/cosx + 1/cosx = (sinx + 1)/cosx multiply top and bottom by (sinx - 1)/(sinx - 1) = (sinx + 1)/cosx * (sinx - 1)/(sinx - 1) = (sin^2 x - 1)/(cosx(sinx - 1)) = cos^2 x/(cosx(sinx - 1)) = cosx/(sinx - 1) = RS
*May 12, 2015*

**math**

I will assume you mean: the sum of the first five terms is 783/2 5th term is 60---> ar^4 = 60 the sum of the first five terms is 783/2 ---> a(r^5 - 1)/(r-1) = 783/2 divide the 2nd by the 1st a(r^5 - 1)/( (r-1)ar^4) = (783/2)÷60 (r^5 - 1)/(r^5 - r^4) = 261/40 261r^...
*May 12, 2015*

**algebra**

1 <---> 11 3 numbers greater than 9 2 numbers less than 3 Prob( as stated) = (3/11)(2/11) = 6/121
*May 12, 2015*

**Algebra II**

again, I think they mean -5(x + 10)^2=390,625 (why would you put a multiplier in front and behind a binomial ?) (x+10)^2 = -78125 which is not possible since the square of anything is positive. So, no solution.
*May 12, 2015*

**Algebra ii**

I have a feeling judging by the numbers that he meant: (x-16)^(4/3) = 81 x - 16 = 81^(3/4) x - 16 = 27 x = 43
*May 12, 2015*

**Pre Calculas**

x^2 = 3^2 + 7^2 x = ....
*May 12, 2015*

**Functions**

given : log2 7 = 2.807 log2 7 = log2 (2x7) = log2 2 + log2 7 = 1 + 2.807 = 3.807
*May 12, 2015*

**Math**

looks like 8 c^6 d^3 to me
*May 12, 2015*

**maths**

.... 1.5 times the sum of the three angle of a triangle ---> 1.5(180) or 270° so sum of 3 angles + x = 360° 270+x=360 x = 90°
*May 12, 2015*

**Probability**

prob(blue) = prob(brown) = 1/2 a) so prob(first child brown) = 1/2 since these prob's are independent, that is, just because the first child has brown eyes, does not mean the second is more likely to have blue eyes so prob(2nd have blue) = 1/2
*May 12, 2015*

**math**

for sequential integer values of n, number = -9n + 17 e.g. n = 3, number = -9(3)+17 =-10
*May 12, 2015*

**ms sue! Algebra help**

You should be familiar with the cosine curve Look at the bottom of this page: http://www.regentsprep.org/regents/math/algtrig/att7/othergraphs.htm The cosine curve runs from -1 to +1. cos(0) = 1 cos(60°) = 1/2 cos(90) = 0 cos(120) = -1/2 etc since secx = 1/cosx at any ...
*May 12, 2015*

**Math**

6. f(-2) = (-2)^2 - 3(-2) + 2 = .... 7. no choices shown "now" the lawn ? You typed it twice, so clearly no typo.
*May 12, 2015*

**Math**

My ruler is marked in inches not months. On mine the 2 inch marks would be 2, 4, 6, 8, ... and 5 1/4 = 5.25, so where do you think it will fall ?
*May 12, 2015*

**Maths**

y = 2x - 4 is not an exponential function, it is linear and its graph is a straight line
*May 12, 2015*

**Math (Riemann Sums)**

I will assume your n = 4 implies you want midpoints as follows 0 -->18 = 9 18 --> 19 = 18.5 19 --> 24 = 21.5 24 --> 12 = 18 so I would have 30(9+18.5+21.5+18) = 2010
*May 12, 2015*

**Math probability**

10 pieces of fruit, 4 apples and 2 apric. prob(apple, then appricot) = (4/10)(2/10) = 8/100 = 2/25 how did you get 3/5 ?
*May 12, 2015*

**Math**

volume of a rectangular prism (a box) = lwh if it is a pyramid with the same base and height V = (1/3)(lwh)
*May 12, 2015*

**geometry**

vertex angle ---- x each of the two equal angles ---- 2x x+2x+2x=180 x = 36°
*May 12, 2015*

**Math**

your statement -2 < π < 2 makes no sense, it simply becomes a false statement: -2 < 3.14.. < 2 I will assume you meant: -2π < Ø < 2π the obvious one: (3,-4π/3) 2 more: (3,-π/3) , (3,5π/6)
*May 12, 2015*

**Geometry**

so your two points are A(a,0) and B(b,0) from A to B = √( (b-a)^2 + 0^2) from B to A = √( (a-b)^2 + 0^2) but (a-b)^2 = (b-a)^2 , (when you square a number the result is positive) e.g. 5^2 = (-5)^2 so the two results are the same
*May 12, 2015*

**Trig identities**

LS = sinx/(1 - cos(-x)) first of all cos(-x) = cosx, so let's change that = sinx/(1 - cosx) now multiply top and bottom by (1+cosx)/(1+cos), thus changing the appearance, but not its value = sinx/(1-cosx) * (1+cosx)/(1+cos) = sinx(1+cosx)/(1 - cos^2 x) = (sinx + sinxcosx)/...
*May 12, 2015*

**Math**

height/50 = tan48° take over
*May 12, 2015*

**Math**

I am not a big fan of double negative-type questions. Perhaps if we change it to: Which is true about the above table? A: It shows a non-linear function. B: The variable x does not increase by 1 each time. C: The rate of change is constant. D: The variable y increases by a the...
*May 12, 2015*

**math**

Since we can't see your diagram, you will have to describe the situation in more detail such as , how far is the spray gun from the wall of the house.
*May 12, 2015*

**algebra**

any horizontal line has equation y = c , where c is the y element of your given point so y = -3 or, the long way: slope of a horizontal line is 0 , then y = 0x + b plug in the given point(5,-3) -3 = 0(5) + b b = -3 y = 0x - 3 y = -3
*May 12, 2015*

**Algebra**

f(x) = 3x - 1 f(0) = 3(0) - 1 = -1 f(3) = 3(3) - 1 = 8 f(z) = 3z - 1
*May 12, 2015*

**Math**

2(x+2)+4x-10x use distribution for the first part = 2x + 4 + 4x - 10x now combine like terms = -4x + 4
*May 12, 2015*

**math**

(2^2)(2^8) = 2^10 so B is the correct answer
*May 12, 2015*

**No - math help please**

It asked for the coefficient of x, which is -7 What you gave is the coefficient of x^2 the correct answer is D
*May 12, 2015*

**Math**

btw, I have a typo, the equation should have said: ax + by + c = 0
*May 11, 2015*

**Math**

Little tricks that can come in handy ... For a linear equation ax^2 + bx + c = 0 the slope is -a/b so the slope of the given line is -3/-2 = 3/2 thus the slope of the new line must be -2/3 But your choice of D has a slope of 3/2, so it can't be D so write the given choices...
*May 11, 2015*

**math**

C) So in effect, the radius of one revolution is 42 cm, and one rotation is 84pi. Multiply 84pi by the number of rotations
*May 11, 2015*

**math**

use the property: ln(e^x) = x 2 = 1 e^(kt) ln 2 = kt t = ln2/k , replace k with the given value
*May 11, 2015*

**maths**

a = 1 , r = -4 you are showing 6 terms, so sum(6) = a(r^6 - 1)/(r-1) = 1((-4)^6 - 1)/(-4-1) = 4095/-5 = -819
*May 11, 2015*

**Pre-calculus ( Absolute value)**

you might plug in x = 5, but x=5 does not satisfy the equation, so it is not a solution. So what if both sides are positive. We know by definition that x-1 > 0 or x>= 1 7+3x = x-1 or -7-3x = x-1 2x = -8 or -4x = 6 x = -4 or x = -3/2 subbing either one of these does not ...
*May 10, 2015*

**math**

... at a rate of 5 inches/hr sounds like a linear rate of change. I will assume that the radius is changing at that rate V = (4/3)pi r^3 dV/dt = 4pi r^2 dr/dt dV/dt = 4pi(100)(5) = 2000pi cubic inches/hr
*May 10, 2015*

**maths**

= 2sqrt(5) - sqrt(5) + 3sqrt(5) = 4sqrt(5)
*May 10, 2015*

**Trigonometry**

RS = (1/2)(cosacosb + sinasinb - (cosacosb - sinasinb) = (1/2)(2sinasinb) = sinasinb = LS
*May 10, 2015*

**Probability**

the second differences are a constant so the relationship is quadratic. the the equation be y = ax^2 + bx + c when x = 1 a+b+c = 20 when x=2 4a+2b+c = 17 when x = 3 9a+3b+c = 13 subtract 1str from 2nd 3a+b=-3 subtract 2nd from 3rd 5a + b = -4 now subtract those last two: 2a...
*May 10, 2015*

**Maths**

the angle between the two directions is 162-25 or 137 Use the cosine law, let the distance between them be d d^2 = 10^2 + 6^2 - 2(10)(6)cos137 = ...
*May 10, 2015*

**Linear Functions**

sketch somethink like y = 2x + 3 (m>0, b>0 ) and see what you get
*May 9, 2015*

**Linear Functions**

e = .04s + 200 see which of your choices match that
*May 9, 2015*

**Math**

(I don't have my calculator with me, so I will describe the method) - find the length of the diagonal of the base using Pythagoras - take half of that length (the midpoint of the base) - use tan^-1 (147/half-length of diagonal)
*May 9, 2015*

**college precalculus I still dont get it**

To be an arithmetic sequence, the difference between any term and its previous term is a constant. e.g. 3, 5, 7, 9 , ... the common difference is 2 To be geometric, if you divide any term by its previous term you will get a common ratio, e.g. 3, 12, 48, ... 12/3 = 4, 48/12 = 4...
*May 9, 2015*

**math**

a) exclude the case where none are cracked Prob(none are cracked) = C(30,0)(.05)^0 (.95)^30 = .... b) follow the above pattern to get Prob(none) + prob(one broken) + prob(two broken) = ..... + C(30,1) (.05)^1 (.95)^29 + .... = ....
*May 9, 2015*

**algebra**

go with Steve, I messed up, right side is .60(20)
*May 9, 2015*

**algebra**

amount of 40% stuff --- x L amount of 85% stuff --- 20-x L .4x + .85(20-x) = .60x
*May 9, 2015*

**Calculus(URGENT PLS!!!)**

how about -e^cosx + c (differentiate it to test my answer)
*May 8, 2015*

**Calculus - Derivative**

2x + r(y)^(-1/2) dy/dx = x dy/dx + y dy/dx (r(y)^(-1/2) - x) = y - 2x dy/dx = (y - 2x)/(r(y)^(-1/2) )
*May 8, 2015*

**Math - Polynomials**

1. The way you typed it should give us 15g + 10k 2. D 3. B Hope you weren't just guessing
*May 8, 2015*

**maths**

the difference between 17^2 and 13^2 is 120. the next perfect square is 121 So we have to add 1
*May 8, 2015*

**7th grade math (probability)**

1-3 are correct #4. you should have divided 4 by 1/6 to get 24 "3" was the event, it happened 4 times, so 4 is the important number last one , I did not check the actual entries, but there are 24 of them
*May 8, 2015*

**Calculus**

here is a picture of what we are doing http://www.wolframalpha.com/input/?i=plot+y%3D+x%5E%281%2F3%29+%2C+y+%3D+x%2C+y+%3D+1 clearly y = x and y = x^(1/3) intersect at (0,0) and (1,1) so outer radius = R = x-1 -->R^2 = x^2-2x+1 inner radius = r = x^(1/3) - 1) --> r^2 = x...
*May 7, 2015*

**Calculus**

V = π∫(y^2) dx from a to b = π∫x^4 dx from 0 to 3 = π[x^5/5] from 0 to 3 = π(243/5 - 0) = 243π/5 cubic units
*May 7, 2015*

**maths**

I see a common factor of 10^7 (5x10^7)+(2.3x10^7) = 10^7(5 + 2.3) = 7.3 x 10^7 your answer should have said 73 x 10^6 In general a number in scientific notation should be a number between 1 and 9 multiplied by a power of 10 so 73 x 10^6, although correct in its value, is not ...
*May 7, 2015*

**Math Please Check My Answer**

From you data it looks like you made 69 choices, thus prob(pink) = 36/69 = 12/23 prob(brown) = 33/69 = 11/23 comparing: theoretical prob(pink) = .5125.. experimental prob(pink) = .5217 not bad
*May 7, 2015*

**Math**

let the base be x by x cm let the height be y xm Volume = (1/3) r^2 h = 216 r^2 h = 648 h = 648/r^2 pick any r, let's say r = 10, then h = 648/100 = 6.48 cm pick x = 12 cm, then h = 648/144 = 4.5 cm As you can see, there is not enough information. as it stands the ...
*May 7, 2015*

**XD**

Suppose it took Alice 4 hrs, when she finished Alice went at 6 km/h Becky went 16 km at 4 km/h Caitlin went 12 km at 3 km/h So for Becky to finish her remaining 8 km would take an extra 2 hrs, but in 2 hrs Caitlin only went 6 more km of her remaining 12 km, so she still has 6 ...
*May 6, 2015*

**XD**

So the total water they have is 2 + 1 3/4 gallons = 15/4 gallons or 3.75 gallons So in effect 3.75 gallons cost $2.00 1 gallon would cost 2/3.75 = .53... so James should receive 2(.5333...) or $1.07
*May 6, 2015*

**Calculus**

did you find their points of intersection? x^2 - 2x = x+4 x^2 - 3x - 4= 0 (x-4)(x+1) = 0 x = -1 or x = 4 effective height of region = x+4 - (x^2 - 2x)= 3x + 4 - x^2 area = [integral] (3x + 4 - x^2) dx from -1 to 4 = [(3/2)x^2 + 4x - (1/3)x^3] from -1 to 4 I will leave the ...
*May 6, 2015*

**Pre-Calculus**

1-|200+||-2|(-5)^3|| 1-|200+||-2|-125|| = 1-|200+||-2(125)| = 1-|200+||-250| = 1 - |200 + 250| = 1 - 450 = -449 I think your |'s are confusing
*May 6, 2015*

**algebra--1 question**

This is called the factor theorem. If the division by some binomial leaves a remainder of zero, then that binomial is a factor the same is true for numbers. e.g. 12÷3 = 4 with Remainder of 0 so 3 is a factor of 12 12÷5 = 2 with remainder of 2, so 5 is NOT a ...
*May 6, 2015*

**Calc**

How do you expect us to know what "table of integrals" you are using ? It is up to you to find the pattern of the given question in your tables.
*May 6, 2015*

**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*