Friday

October 28, 2016
Total # Posts: 45,417

**math**

you're right - you do need help...

*October 3, 2016*

**Algebra**

The area is length * width: (2x+5)(8) = 16x+40 Use that in B, and then solve for x if 16x+40 = 160

*October 3, 2016*

**Math adv functions**

a little synthetic division shows that it is not. However, it is a factor of x^9+5b^2x^7+5bx^8+b^9

*October 3, 2016*

**Math**

Start a table of the powers of 11 n 11^n 1 11 2 121 3 1331 4 14641 The last 2 digits just cycle through 11 21 31 ... 91 01 11 21 ... So, 11^2016 ends in 61 Or, you might find this article on modular arithmetic useful: https://www.khanacademy.org/computing/computer-science/...

*October 3, 2016*

**science**

what do you think? If you toss in something light, like a cotton ball, does it float or sink?

*October 3, 2016*

**math**

y = a√x + bx y' = a/(2√x) + b Since the normal at x=1 has slope 1, the tangent has slope -1. So, y'(1) = a/2 + b = -1 b = -(a+2)/2 y(1) = a - (a+2)/2 = (a-2)/2 The normal line through (1,(a-2)/2) is thus y-(a-2)/2 = 1(x-1) This passes through (0,-14), so -...

*October 3, 2016*

**math**

is the : supposed to be division? If so, 1/(-1) + 0/4 - (-4)x(-1) = -1 + 0 - 4 = -5

*October 3, 2016*

**Math**

uhhh, that's what I did, right?

*October 3, 2016*

**Math**

you can approximate it using logs log(11^2016) = 2016 * log11 = 2016*1.04139 = 2099.4476 so, 11^2016 ≈ 2.80319 * 10^2099 the exact value is at http://www.wolframalpha.com/input/?i=11%5E2016

*October 3, 2016*

**Math**

you're welcome. Tricky problem, and easy to misinterpret, as I showed.

*October 3, 2016*

**Math**

You are right. They started out as 99% water, so there was .99 * 16 = 15.84 lbs water .01 * 16 = 0.16 lbs flesh When they have dropped to 80% water, the 0.16 lbs flesh is still there, but it is now 20% of the weight. So, 0.16 = 0.20x x = 0.8 so, the cucumbers now weigh 0.8 lbs.

*October 3, 2016*

**Math**

.80 * 16 lbs

*October 3, 2016*

**Math**

9*134 = 1206 9*322 = 2898 So, subtract all the multiples of 9 from the total sum: ∑[k=1200,2900] k - ∑[k=134,322] 9k = 3 487 050 - 387 828 = 3 099 222

*October 3, 2016*

**Algebra**

area = width * height = (2x+5)(5) = 10x+25 then solve for x if 10x+25 = 160

*October 3, 2016*

**Algebra 2**

B does the compression, but not the reflection. Reflection through the x-axis takes (x,y) -> (x,-y)

*October 3, 2016*

**Ap maths**

as usual, google is your friend. You can start here: http://www.meritnation.com/ask-answer/question/if-a-b-and-c-are-in-g-p-and-a1-x-b1-y-c1-z-prove-that/sequences-and-series/6204621

*October 3, 2016*

**Calc 2**

the graphs intersect at (-1,1) and (2,4) Recall that the volume of a shell of thickness dx is v = 2πrh dx So, to rotate around the line x=2, v = ∫[-1,2] 2πrh dx where r = 2-x and h=(x+2)-x^2 v = ∫[-1,2] 2π(2-x)(x+2-x^2) dx = 27π/2 Just to verify...

*October 3, 2016*

**Math**

no idea what you mean by more 0.7 and 5/8

*October 3, 2016*

**Math**

add up the fractions and subtract from 1 That is how much was left. Equate that to 26. For example if, 2/13 was left, then 2/13 x = 26 x = 169

*October 3, 2016*

**Math**

the [] are just like () but make it easier to read than ((8^2-4)-6)/6 You will also see braces {} if there are even more levels of nesting. Anyway, treat them all the same. Your answer of 9 is correct

*October 3, 2016*

**Math**

ok - now what?

*October 3, 2016*

**Algebra**

If you let u = x^(1/4) your equation becomes much easier to look at: x^(1/2)-3x^(1/4)-4 = 0 u^2 - 3u - 4 = 0 solve for u, and then x = u^4

*October 3, 2016*

**Physics**

yes. But it's probably better just to say 146.5 km/hr the numbers are not so big as to need scientific notation, and they were all defined with one decimal place of accuracy.

*October 3, 2016*

**physics**

50m, of course. you want to rephrase the question? also, recall that the height h is h = 50 - 4.9t^2 use that t in figuring distance = speed * time

*October 3, 2016*

**Math**

12 farmers * 3 days = 2 hectares multiply by 5/2 and you have 12(5/2) farmers * 3 days = 5 hectares Now on the left, multiply by (3/10)(10/3): 12(5/2)(3/10) farmers * 3(10/3) days = 5 hectares 9 farmers * 10 days = 5 hectares or 12f * 3d = 2h 9f * 4d = 2h 9f * 10d = 2(5/2) = 5h

*October 3, 2016*

**Linear or Nonlinear, Order.**

if you review your text, you can easily find what the order of a DE is. (think of the order of a polynomial). As for linear, a DE is linear just as a polynomial is linear. So, take your best guess, and then type your DE in at wolframalpha.com and it will tell you whatcha got. ...

*October 3, 2016*

**math**

no. You want the equation which is true of you sub in -3 and 4. -3x+4y = -3(-3)+4(4) = 9+16 = 25 Substitute the values for x and y into the other equations and see which produces the result on the right. For example, it is not A, because that would become 4 = -3 Plus, it might...

*October 3, 2016*

**Geometry**

see related questions below

*October 3, 2016*

**Calculus II**

depends on the interval. In regions of low curvature, fewer trapezoids are needed.

*October 3, 2016*

**math**

if y is the 2nd number, then y=3x

*October 3, 2016*

**math**

36/24 = 1.50 lots of other, I'm sure.

*October 3, 2016*

**science**

only indirectly volume is space matter is mass to relate the two, you have density, which is mass per unit volume

*October 3, 2016*

**Math,Algebra**

correct That's 76m down, or at a level of -76m

*October 3, 2016*

**Math,Algebra**

well, he rose 3*7 = 21m where does that leave him?

*October 3, 2016*

**math**

no way k/x^2 -> ∞ as x->0

*October 3, 2016*

**Math**

in word problems, "of" almost always means "times" for calculations. (2/7)*(3/4) = 6/28 = 3/14

*October 3, 2016*

**Algebra**

easy way: compare the slopes of the lines. If different, they must intersect exactly once.

*October 3, 2016*

**math**

Or, consider the probability of drawing 6 consecutive winning numbers without replacement: 6/44 * 5/43 ... * 1/39 = 6!/(44*...*39) = 1/C(44,6)

*October 3, 2016*

**math**

no idea what the length of the chalk stick is, since you have given neither density nor size. All we know is that the carbon is 3/25 = 12% of the total mass.

*October 3, 2016*

**math**

1/3 + 1/4 + 1/8 = 19/24 so, 5/24 of the land is 18 hectares.

*October 3, 2016*

**Maths**

first, I think you mean to say that log 2 = 0.3010 log 3 = 0.4771 Now: 72 = 2^3 * 3^2 so log 0.72 = 3log2 + 2log3 - 2

*October 3, 2016*

**math**

now subtract the initial 10,000 the rest is the income.

*October 3, 2016*

**Physics**

36 km/hr = 10 m/s so, the acceleration is a = (10m/s) / (5s) = = 2 m/s^2 distance covered in 1st 5 seconds: s = 1/2 at^2 = 25m at 10 m/s, it travels another 10*5 = 50 m the distance braking is the same as the first 25m, so the total distance is 100m

*October 3, 2016*

**maths**

the two numbers are in the ratio 4:3 divide 84 into 7 parts. see where that gets you.

*October 3, 2016*

**Algebra2**

It all comes with experience. You might just note that the powers of i cycle in periods of 4: i^-4 = 1 i^-3 = 1/i^3 = 1/-i = i i^-2 = 1/i^2 = -1 i^-1 = 1/i = -i i^0 = 1 i^1 = i i^1 = -1 i^3 = -i i^4 = 1 ...

*October 3, 2016*

**Algebra2**

(-5+i)/2i = -5/(2i) + 1/2 Now, 1/i = -i, since i^2 = -1 Thus we end up with 1/2 + 5/2 i or (1+5i)/2

*October 3, 2016*

**Algebra2**

Simplify the expression -5+i/2i -5+i over 2i

*October 3, 2016*

**math**

since integers are rational numbers, you also have -3, -2, -1, 0 put any denominators you want on those, too.

*October 3, 2016*

**Math**

b^2-24b+135 = (b-9)(b-15) So, the extrema are at b=9 or b=15. Naturally, at b=15, a=0, so the product is a minimum At b=9, a=6, and the product is 6^2*9^3 = 26244

*October 3, 2016*

**Calculus**

Once you have convinced yourself that the derivative really is -3(x^2-3x+1)/(x^2-x+1)^3 f(x) is increasing where f'(x) is positive Note that the denominator is always positive, so f' is positive when the numerator is positive. That is, when x^2-3x+1= is negative. That ...

*October 2, 2016*

**Calculus**

You need to simplify your derivative a bit. It boils down to -3(x^2-3x+1)/(x^2-x+1)^3 That's a bit easier to work with. See where that takes you.

*October 2, 2016*

**Math 115**

Scott gave you an answer. How do you get yours?

*October 2, 2016*

**unt**

p(heads) = 1/2 on each throw. So, p(9 heads) = (1/2)^9 = 1/512

*October 2, 2016*

**Math precalculus**

since C is a function of revenue, C(R(x)) = 0.30R(x) = 0.30(80x) = 24x the "x" in this equation is the number of books.

*October 2, 2016*

**Physics**

You want the distances to be the same after t hours. So, noting that 6.5 m/s^2 = 23400 km/hr^2 105t = 40t + 23400/2 t^2 t = 1/180 hr So, you overtake the train after 0.583 km I hope you were not uncomfortable with the unusual units; you can always convert the speeds to m/s if ...

*October 2, 2016*

**Algebra**

since distance = speed * time 6.5x + 6.5(x+32.4) = 390

*October 2, 2016*

**Math graphs, dot, Venn**

I agree

*October 2, 2016*

**calculus 1**

y=4x^3−19x+40 y' = 12x^2-19 So, at any point (x,y) the slope is 12x^2-19 Using the point-slope form y-2 = y'(x-2) 4x^3−19x+40-2 = (12x^2-19)(x-2) 8x^2(3-x) = 0 x = 0,3 So, the tangents through (0,40) and (3,91) pass through (2,2) The lines are thus y-40 = -...

*October 2, 2016*

**Math**

so, did you make a number line and decide on the units? what are they talking about?

*October 2, 2016*

**math (caculus limits)**

true. Go check out the definition of limits or continuity.

*October 2, 2016*

**math**

You understand what consecutive integers are. Now just write down the conditions as algebra: x + x+1 = 4(x+2)-177 now solve for x.

*October 2, 2016*

**math**

1<x<2

*October 2, 2016*

**Calculus**

how about the good old f(x) = x^3 at x=0, f'=0, but it is an inflection point. the problem with your function is that f(0) is not even defined!

*October 2, 2016*

**Math (Domain and range)**

the interval (5,6] is excluded from the range, because of the jump at x=0.

*October 2, 2016*

**Math**

the number of students does not matter. If there are x boys, then x/(x+2x) = x/3x = 1/3

*October 2, 2016*

**Math**

since there are no repeats, 3 letters, 1st vowel: 5*25*24 5 digits, middle even: 5*9*8*7*6 (consider picking the even digit first) 2 letters: 23*22 1 digit: 5 so I get only 114,768,800,00

*October 2, 2016*

**Math**

why not show your work? The discriminant is k^2-36 Now, what does that tell you about the number of roots?

*October 2, 2016*

**math**

there are lots of online calculators, such as this one, which shows all the operations. http://www.dougbabcock.com/matrix.php

*October 2, 2016*

**maths(Quantitative Method)**

just add a 3x3 array of zeroes on the right

*October 2, 2016*

**Math**

sorry - no graphs. But something like y > mx+b will be the shaded area above the line y = mx+b

*October 2, 2016*

**math (stats)**

you can just as easily consider the % values as integers. Then just count the ones you need, out of 100

*October 2, 2016*

**algebra**

enter your data here to see all the details http://www.gregthatcher.com/Mathematics/GaussJordan.aspx

*October 2, 2016*

**math**

check the 68% rule

*October 2, 2016*

**math**

a = πr^2 now just substitute in x or (x+5)

*October 2, 2016*

**value**

h(h+3)/2=44

*October 2, 2016*

**maths**

If you have Ax=B, then x = A^-1*B Here, A^-1 = http://www.wolframalpha.com/input/?i=inverse+%7B%7B2,-1,3%7D,%7B1,1,1%7D,%7B1,-1,1%7D%7D

*October 2, 2016*

**Math**

p^4+m^4 = (p^2+m^2 i)(p^2 - m^2 i) = (p-m√i*i)(p+m√i*i)(p+m√i)(p-m√i) = (p-m√i^3)(p+m√i^3)(p+m√i)(p-m√i) = (p-m√-i)(p+m√-i)(p+m√i)(p-m√i) I assume you can figure out what √i and √-i are. (de ...

*October 2, 2016*

**Math**

what a ripoff!

*October 2, 2016*

**Maths**

grrr. pi, not pie! split it up and you have dx/(x+2) = sin^2(2t) dt ln(x+2) = 1/8 (4t-sin(4t))+c x+2 = c e^(1/8 (4t-sin(4t)) at (0,0) we have 2 = c, so x = 2e^(1/8 (4t-sin(4t)) - 2

*October 2, 2016*

**calculus**

surely you can graph a simple parabola. Let the rectangle have height 2y and width a-x The area is then A = 2xy = 2(a - y^2/4p)y = 2ay - y^3/2p dA/dy = 2a - 3y^2/2p dA/dy = 0 when y = 2√(ap/3) now just figure A=2xy there.

*October 2, 2016*

**Geometry**

r^2 = 14^2 + 18^2

*October 2, 2016*

**Math**

well, 0 is the smallest digit

*October 2, 2016*

**Math 😢😢😢😢😢 Help**

on the first draw, p(red) = 5/38 Now, for the 2nd draw, what is p(red)? One red marble is now missing.

*October 2, 2016*

**Math (Perpendicular equation)**

the slope is good, so why not just use the point-slope form? y - 9/10 = (-4/6) (x - 4/5) The only thing I would do is use -2/3 for the slope. Unless they say they want a particular form for the equation, use the one most convenient.

*October 2, 2016*

**Math**

why not show your work? The discriminant is k^2-36 Now, what does that tell you about the number of roots?

*October 2, 2016*

**Math**

well, the altitude is √(a^2 - (c/2)^2)

*October 1, 2016*

**Math**

the law of sines says that the angle opposite side a will be the largest. Use the law of cosines to find that angle.

*October 1, 2016*

**Math (Secant Lines)**

the slopes look good. The secant through (1,1) doesn't help much, but the lines through (3,√3) and (5,√5) bracket the tangent at (4,2). Pick points closer to (4,2) to refine your value.

*October 1, 2016*

**Techno missioninternational school**

.08*4 x = .09*2 (3000-x)

*October 1, 2016*

**Trigonometry**

let's get rid of all the - signs sin(x) tan(x) + cos(x) = sec x sin^2x/cosx + cosx = secx (sin^2x + cos^2x)/cosx = secx now what do you think?

*October 1, 2016*

**Trigonometry**

pick an angle and show that the equation fails. tan(pi/2) ≠ 2 tan(pi/4)

*October 1, 2016*

**Math Idk?**

right

*October 1, 2016*

**Math Idk?**

how many numbers less than 8? divide by 10

*October 1, 2016*

**Math Help!**

how many did not get B? how many total? divide

*October 1, 2016*

**Math**

If you build a Venn diagram for this, you can just read off the numbers. Start with the 5 who like all three sports, and subtract that from the regions which like two or one. The 9 who like nothing don't count.

*October 1, 2016*

**Physics**

see your previous post, in the related questions below. Where did you get stuck?

*October 1, 2016*

**Physics**

cool.

*October 1, 2016*

**Physics**

transverse speed is dy/dt, so x is constant. dy/dt = (3.6cm)(-3.1)cos(2.7x−3.1t +0.97) at x = 0.5, that is dy/dt = -11.16 cos(2.32-3.1t) To find maximum speed, you need y" = 11.16(-3.1) sin(2.32-3.1t) = 0 clearly that is at 2.32-3.1t=0 or pi. t = 0.75 or 1.76 we ...

*October 1, 2016*

**math**

not sure what techniques you have to use. You can use Descartes' Rule of Signs, or the signs produced in synthetic division to get a handle on the bounds, but otherwise you may be stuck with iterative numeric techniques. If you have calculus under your belt, then we can ...

*October 1, 2016*