Thursday

October 27, 2016
Total # Posts: 45,368

**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*

**math**

start listing some doubles: 1 = 2^0 2 = 2^1 4 = 2^3 see a pattern? But you started with 25 instead of 1, so... But there are two possible functions. How much was given each year, or how much in total had been given by the nth year.

*October 1, 2016*

**MATH**

That is not a problem. It is an equation. The problem is to find what you want to do with it. I'll assume you want to solve for y. I'll also assume that by log you mean natural log. If so, then z=log(e^(5y)) = 5y y = z/5 If by chance you meant log base 10, then 10^z = ...

*October 1, 2016*

**Math**

see previous post and work it similarly

*October 1, 2016*

**Math**

(x+2)^3 * x

*October 1, 2016*

**Algebra**

since the coefficients are real, complex roots occur in conjugate pairs. So, 2+i is another root. Similarly, since the coefficients are rational, we need to balance that √2 with -√2. f(x) = (x-(2-i))(x-(2+i))(x-√2)(x-(-√2)) = ((x-2)+i)((x-2)-i)(x-√...

*October 1, 2016*

**Algebra 2B**

no idea what −< < 1 0 m means.

*October 1, 2016*

**algebra**

the domain is the set of 1st elements (x) of each pair. the range is the set of 2nd elements (y). It is a function if no x is paired with more than one y. That is, if each pair has a unique x.

*October 1, 2016*

**Math**

That's funny -- I get 1400 * 20 = 28,000 !

*October 1, 2016*

**Pre Cal help please!!**

since the left limit does not equal the right limit, lim as x->2 does not exist. And of course, f(2) is not even defined.

*October 1, 2016*

**Physics**

#1 It must fall, because of gravity.

*October 1, 2016*

**Trigonometry**

the amplitude is 8, so y = 8cos(kx) or 8sin(kx) It starts with y(0) = -8, so y = -8cos(kx) The period is 1/2, so 2π/k = 1/2 y = -8cos(4πx)

*October 1, 2016*

**Physics**

speed = distance/time so, what is the round-trip distance?

*October 1, 2016*

**maths**

ummm (x^3+3x^2y+3xy^2+y^3) = (x+y)^3 (x^3+y^3)(x^3-y^3) = (x+y)(x^2-xy+y^2) (x-y)(x^2+xy+y^2)

*October 1, 2016*

**school**

(a) a = (11-13 m/s)/2.4s = -2/2.4 m/s^2 (b) v = 11 - at, so use t=1.5

*October 1, 2016*

**simpson**

If y = ∑an x^n then y' = ∑n an x^(n-1) y' = 2x cos(x^2) You know the power series for cos(u), so expand both and equate coefficients to get a recurrence relation. google can show you lots of examples of solution by power series

*October 1, 2016*

**maths**

This is another homogeneous equation. Substitute y = vx and you end up with dv/√(1+v^2) = -1/x dx

*October 1, 2016*

**maths sir-reiny help calculus**

step-by-step requires a paid subscription. But, note that y' = xy/(x^2-xy+y^2) This is homogeneous, so let y=vx Then y' = v + xv' v + xv' = vx^2/(x^2-vx+x^2v^2) v + xv' = v/(v^2-v+1) xv' = (v^2-2v+1)/(v^2-v+1) (v^2-v+1)/(v-1)^2 dv = -1/x dx Now just do ...

*October 1, 2016*

**chemistry**

convert the mass to moles write the balanced equation see how much excess Br remains from 40g of CaBr2 -- call that x grams Multiply that by 10 lbs/x g Good practice in unit conversions!

*October 1, 2016*

**maths**

y = kx^2 when x is doubled, you have k(2x)^2 = 4kx^2 = 4y so, y has grown by 300%

*October 1, 2016*

**Math Help!**

you cannot do that integral with elementary functions. Here's what wolframalpha says: http://www.wolframalpha.com/input/?i=integral+sin(x%5E2)+dx

*October 1, 2016*

**maths need help**

f(0) = f(2π) = 1 so the condition is satisfied. So, now you want c such that f'(c)=0 f' = cosx - sinx f' = 0 at x = π/4 π/4 is in the interval [0,2π], so ta-da!

*October 1, 2016*

**Math (Expanding logarithmic expression)**

no, you cannot. ln(x) + ln(y) = ln(xy) ln(x+y) is NOT ln(x) + ln(y) instead of expanding the polynomial, you could do ln[(x^2+1)(x-1)] = ln(x^2+1) + ln(x-1)

*October 1, 2016*

**nts**

first step: study

*October 1, 2016*

**Math Help ASAP SETS & Probability**

same song, different verse

*October 1, 2016*

**Probability Help ASAP!**

(total females)/(total students)

*October 1, 2016*

**Probability**

(total who got A)/(total students)

*October 1, 2016*

**Math - eh?**

eh? eh? In number and it's our food value are equal eh?

*September 30, 2016*

**Physics**

s = vt + a/2 t^2 Now plug in your numbers for v,a,t

*September 30, 2016*

**physics**

(-26900/60*2pi rad/s)/(8.00s) = -352.12 rad/s^2

*September 30, 2016*

**Sets & Probability math Help please**

206/(206+184)

*September 30, 2016*

**PROBABILITY MATH HELP!!!!!**

first off, any probability is at most 1. (c) There is only one number on a die which is greater than 5. So, of the 6 events, only 1 is a success. So, p(x>5) = 1/6

*September 30, 2016*

**PROBABILITY MATH HELP!!!!!**

well, there are 6 possible events. How many for success in each question?

*September 30, 2016*

**Algebra**

A and D are clearly out, as there is no addition. Now check your notes for the meaning of the other properties.

*September 30, 2016*

**math**

how much area did your hike cover? The greater the area, the more likely you encounter 9 people.

*September 30, 2016*

**trigonometry**

oops. That's 2π/15

*September 30, 2016*

**trigonometry**

a = 1/2 r^2 θ, so 1/2 r^2 * π/15 = 426

*September 30, 2016*

**Algebra2**

Thank you

*September 30, 2016*

**Algebra2**

looks good

*September 30, 2016*

**Algebra2**

What is the equation, in standard form, of a parabola that contains the following points? (-2,-20),(0,-4),(4,-20) 1- y=-2.5x^2+5x 2-y=-x^2+4x-4 3- y=-2x^2+4x-4 4-y=-2.25xx^2+4.5x-2 My answer is 3

*September 30, 2016*

**Math**

h = 15 inches, not 1.3

*September 30, 2016*

**Stats**

you can play around with Z table stuff here: http://davidmlane.com/hyperstat/z_table.html

*September 30, 2016*

**Physics**

how long does it take to fall 0.85m? 4.9t^2 = 0.85 use that value of t to figure the velocity: vt = 4.45

*September 30, 2016*

**Math**

as google will provide, there are many similar exercises online. You might start here: http://math.stackexchange.com/questions/79282/solving-simultaneous-congruences

*September 30, 2016*

**Physics**

F=ma, so a = F/m so, greater mass, less acceleration

*September 30, 2016*

**algebra 2**

7/∛3 + 2 you want 3 in the bottom, so you need to multiply by ∛3^2 7∛9/3 + 2 = (6+7∛9)/3

*September 30, 2016*

**Stats**

p(x=0) must be less than 1

*September 30, 2016*

**maths help**

2.288/4.288 = 0.533 How did you get 0.77?

*September 30, 2016*

**math**

actually, I guess if 3070 is allowed, so is 7030 If all digits must be unique, then I guess 3214 is the only choice.

*September 30, 2016*