Thursday

February 23, 2017
Total # Posts: 48,712

**algebra**

y(x(t)) = ln(2x(t)) = ln (2*3e^(t/1.7)) = ln6 + ln e^(t/1.7) = t/1.7 + ln6

*February 18, 2017*

**Algebra**

google is your friend. This is but one of many discussions on the topic. http://www.web-formulas.com/math_formulas/geometry_surface_of_cone.aspx

*February 18, 2017*

**science**

resistance = (resistivity * length)/area so, just plug in your numbers... watch the units.

*February 18, 2017*

**Math**

That's what I get, too.

*February 18, 2017*

**science**

You need 2 H for each CO3, so 2HCl + K2CO3 -> 2KCl + H2CO3

*February 18, 2017*

**electronic**

sounds like you just have to plug in the numbers ...

*February 18, 2017*

**MATH**

As Crocodile Dundee would say, Now that's a detour! (eh?)

*February 18, 2017*

**MATH**

cosA = 1/2 A = ?/3 4A = 4?/3 cos4A = -1/2

*February 18, 2017*

**Science**

NO is 2/5 of the output of 10 moles. Since the original 9 moles occupied 27 liters, the 10 moles occupy 30 liters. So, NO occupies 2/5 * 30 = 12 liters. This assumes that the H2O is also a vapor.

*February 18, 2017*

**Algebra**

2x+2y = 28 so, y=14-x for the area, a = xy = x(14-x) This is just a parabola,so find its vertex.

*February 17, 2017*

**Math**

what were the possible scores on the dart board?

*February 17, 2017*

**Math**

yes.

*February 17, 2017*

**Physics**

23 * 24 * 8/1000 = 4.4¢

*February 17, 2017*

**um**

at wolframalpha.com, type in arctan(8) Or, learn to use your calculator ...

*February 17, 2017*

**precalculus**

e^(.08t) = 2 The initial amount does not matter.

*February 17, 2017*

**geometry**

in a 30-60-90 right triangle, the ratio of the sides is 1:?3:2 m?L = 30°, so the short leg is 9. The sides are thus 9,9?3,18 and the perimeter is 27+9?3 Looks like you need to review the standard triangles...

*February 17, 2017*

**geometry**

note that in a 45-45-90 right triangle, the sides are in the ratios 1:1:?2 So, draw the figure, label the known side, and then you can get the others.

*February 17, 2017*

**physical science**

more likely, something metric ...

*February 17, 2017*

**Esol**

correct.

*February 17, 2017*

**math**

uh, I'd guess 20/8

*February 17, 2017*

**Algebra**

f(x) = -5(3^x) f(0) = -5(3^0) = -5(1) = -5 f(1) = -5(3^1) = -5(3) = -15 f(2) = -5(3^2) = -5(9) = -45 the graph is at http://www.wolframalpha.com/input/?i=-5(3%5Ex)

*February 17, 2017*

**Geometry**

PN^2 = 17^2-15^2 = 64 PN = 8 So, NQ = 39-8 = 31 QR^2 = 31^2+15^2 = 1186 QR = 34.438

*February 17, 2017*

**Math**

Alkesh borrowed -- x Sanjay borrowed -- 2x So, how much interest did Sanjay pay? see where that takes you. (I think the actual question is garbled...)

*February 17, 2017*

**math**

A = ?ab Note that for a circle, a=b, so A = ?a^2

*February 17, 2017*

**math**

dy/dt = y/4 dy/y = 1/44 dt lny = t/4 + c y = c*e^(t/4) y(0)=20, so c*e^0 = 10 c = 20 y = 20e^(t/4) You are correct.

*February 17, 2017*

**Geometry**

since the diagonals bisect each other, AE = EC 3x+12 = 27 ...

*February 17, 2017*

**Vector**

Assuming it is in the same direction, then if p is the vector to P, then p+v = [-11,-1] Q = (-11,-1) Q could also be the end point of p-v.

*February 17, 2017*

**math**

"more" means you are going to add. Add what to what?

*February 17, 2017*

**Math**

4.75 = 4 3/4 = 19/4 6 1/8 = 49/8 6.3 = 63/10 10 1/2 = 21/2

*February 17, 2017*

**Stat**

2(26^2 + 26^3) = ?

*February 17, 2017*

**Algebra**

(x-1/2)-(x-2/2)+(x-3/2)-...-(x-100/2) x-x+x-x+...+x-x - 1/2 + 2/2 - 3/2 + ... - 99/2 + 100/2 the x-x+x-x terms cancel out, and we are left with 1/2 (-1+2 -3+4 ... -99+100) = 1/2 (1+1...+1) (50 times) = 1/2 * 50 = 25

*February 17, 2017*

**Maths**

first, how is the "rank" of a word defined?

*February 16, 2017*

**Math**

$22/player, so ...

*February 16, 2017*

**Statistics**

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

*February 16, 2017*

**math**

using similar triangles, if he is x meters from the tree, (x+3.5)/28 = 3.5/1.5

*February 16, 2017*

**Math Help**

Or, consider drawing 4 cards with no replacement. Then the probability of getting all reds is 26/52 * 25/51 * 24/50 * 23/49 = 0.05522 Note that C(26,4) = 26*25*24*23 C(52,4) = 52*51*50*49 You can see that the division shown by Reiny produces the same fractions.

*February 16, 2017*

**math**

1 to any power is still 1. 2^-3 = 1/8 So, you have 4 * 1/8 * 1 = 1/2 = 2^-1

*February 16, 2017*

**math**

2/3 = 1/3 + 1/3 so, it has doubled, making a 100% increase. a 33.3% decrease would mean subtracting 1/3 of the original 1/3, or 1/9 so, 1/3 to 2/9 is a 33.3% decrease

*February 16, 2017*

**Algebra**

If the number is ab, b = a+7 10b+1 = 3(10a+b + a+b) 81 = 3(18 + 9)

*February 16, 2017*

**Math**

well 2×15×2 = 60

*February 16, 2017*

**Algebra 1**

Looks like you're a bit off. See http://www.wolframalpha.com/input/?i=solve+y%3D0.081+*+x+%2B+215.378,+y%3D0.222+*+x+-+43.829 Doing the substitution, I get y=0.081 * x + 215.378 so, 0.081x + 215.378 = 0.222x - 43.829 0.141x = 259.207 x = 1838.3475 y = 364.2841 Not sure how...

*February 16, 2017*

**Chem**

N comprises 251/(322+146+251) = 34.9% of the mixture, so ... PV=kT so use that to get V.

*February 16, 2017*

**Math**

well, each side is 17/?2

*February 16, 2017*

**math**

disregarding the units, 2 pi r = 200 pi r = 100

*February 16, 2017*

**Chem**

well, what is the molar mass of NaHCO3?

*February 16, 2017*

**Calculus**

The area is an 8x4 rectangle and a 4x4 square, = 48 Divide that by the interval width and you get 6.

*February 16, 2017*

**physics**

F=ma, so a = 15/4 m/s^2 v=at, so v increases by 4 * 15/4 = 15 m/s p=mv, so p changes by 4*15 = 60 kg-m/s

*February 16, 2017*

**math**

(-6*4x^2*y^3/27xy^4)^1/3 = ((-6/27) x/y)^1/3 = -1/3 ?(6x/y)

*February 16, 2017*

**Math**

no idea on 1 & 3. Picture needed. The others are correct. On #6, it could be any of A,B,C depending on the figure. A is the most general.

*February 16, 2017*

**math**

5+3.25x = 18

*February 16, 2017*

**Math - Sequences**

well, what is 15+1.5? That's the 2nd term, clearly.

*February 16, 2017*

**math**

bh/2 = 110 10h/2 = 110 ...

*February 16, 2017*

**Math (Algebra 2)**

so, why not show your work? P(1+.0939)^10 = 20000 Now just solve for P.

*February 16, 2017*

**math**

x = 3(x+3)-3(x-3) x=18

*February 16, 2017*

**math**

the triangle is half the area of the trapezoid.

*February 16, 2017*

**Math**

ever hear of < and <= and > and >= ? Other than that your answers are ok, assuming the 60 in #2 is a typo.

*February 16, 2017*

**math**

(x,y) is symmetric with (-x,-y) so, what do you think?

*February 16, 2017*

**math**

for any interest rate r compounded n times per year, and time t years, A = P(1 + r/n)^(nt) so, plug in your numbers.

*February 16, 2017*

**urgent math help plz !!**

Assuming you meant sin?=3/4 The hypotenuse is 4, so the other leg is ?(16-9) = ?7 In QII, x<0. Since cos? = x/r cos? = -?7/4 You should immediately have known your answer was wrong, because sin^2? + cos^2? = 1

*February 16, 2017*

**maths**

Draw a circle with bc as diameter. Chords ac and db are the same length, so the subtend the same central angle. So, ac is parallel to bd, and abcd is a rectangle. So you have SAS and congruent triangles.

*February 16, 2017*

**P4 maths**

3x = x/2 + 10 x = 4

*February 16, 2017*

**Math**

(x-1)/2+(x-2)/2+(x-3)/2+...(x-100)/2 1/2 (x-1 + x-2 + x-3 + ... + x-100) = 1/2 (x+x+x... - (1+2+3..+100)) = 1/2 (100x - 100*101/2) = 50x - 2525

*February 16, 2017*

**Math - Calculus**

since |sinx| <= 1, x^2 sin(1/x) < x^2. So, since x^2 -> 0, so does x^2 sin(1/x) x^2 sin(1/x) does not exist when x=0, but since f(0)=0, f is continuous. [(0+h)^2 sin(1/(0+h)) - 0^2*sin(1/0)]/h = [h^2 sin(1/h) - 0]/h = h^2 ((1/h) - 1/3! (1/h^3) + ...)/h = (h - h/3...

*February 16, 2017*

**pre algebra**

note that as x changes by 1, y changes by 3 So, start with y=3x But, y(0) = 8, so use y=3x+8 check to be sure it fits all the pairs. It does.

*February 16, 2017*

**Math**

correct.

*February 16, 2017*

**Maths**

value is .85 * .88 * .88 = 0.6582 so, it has lost 34.18% Looks like you'd better show your work, huh?

*February 15, 2017*

**Calculus**

correct

*February 15, 2017*

**precalculus**

GCD(42,70) = 14, so ...

*February 15, 2017*

**math**

If you can construct a 60°, bisect it and you have your 30° angle. Build from that.

*February 15, 2017*

**Calculus Question! ASAP!**

you can do the trig stuff, but why bother? let u = 9-x^2 du = -2x dx and the integrand becomes -1/2 u^(-1/2) du and integrates to - u^(1/2) = -?(9-x^2) As for the trig, you cannot take ?(1-sec^2) since sec^2 is always greater than 1, and you don't have a real value. I'...

*February 15, 2017*

**Math**

I'd suggest 4, since it is the greatest common factor of 20,32,64

*February 15, 2017*

**Math**

just multiply 4x5 by 1/2 and 5/4: 2x2.5 and 5x6.25

*February 15, 2017*

**Calc**

f(x) = ?[x,x^8] ln(t) dt The 2nd fundamental theorem is really just the chain rule. f'(x) = ln(x^8)*8x^7 - ln(x)*1/x = 8lnx*8x^7 - ln * 1/x = lnx (84x^7 - 1/x) This works because if g(t) = ?lnt dt g'(t) = ln(t) So, f(x) = g(x^8) - g(x) so, f'(x) = g'(x^8)*8x^7...

*February 15, 2017*

**Math**

yes.

*February 15, 2017*

**too-hard probability sir damon/reiny/steve help**

I get 5/14 = 0.3571 Damon's answer above is P(b=2)/P(w?0) = 0.3546 Seems they ought to be the same ...

*February 15, 2017*

**Math**

1. use the Angle Bisector Theorem. 2. The volume of oil is the area of a circular cap times the length. So, the the formula for the area of a circular cap. Then if the oil volume is v, the depth would have been (v/60?)*15 3. Consider the problem in 2D, and draw a rectangle. If...

*February 15, 2017*

**Math**

m(PQS) + x = 180

*February 15, 2017*

**maths**

a(r^4-1)/(r-1) = 30 a + ar^3 = 18 (r^4-1)/((r-1)(1+r^3)) = 5/3 3r^4-3 = 5r^4-5r^3+5r-5 2r^4-5r^3+5r-2 = 0 (r-1)(r-2)(r+1)(2r-1) = 0 r = 1/2, 1, 2, -1 r=1,-1: extraneous solutions r=2: 2,4,8,16,... r=1/2: 16,8,4,2,...

*February 15, 2017*

**math**

ever think of using math notation instead of words? f(x) = 4x for x <= 3 7-x for x > 3 ?[1,7] f(x) dx = ?[1,3] 4x dx + ?[3,7] 7-x dx = 2x^2[1,3] + 7x - x^2/2 [3,7] = [(2*3^2)-(2*1^2)]+[(7*7-7^2/2)-(7*3-3^2/2)] = 16+8 = 24

*February 15, 2017*

**math**

3 log(u^2/v) 3(2logu - logv)

*February 15, 2017*

**math 103**

the lines intersect at (15,20) The new line has slope -3/5, so it is y-20 = -3/5 (x-15) now massage that into the form you want.

*February 15, 2017*

**Math**

not 810, but vh=810*cos42 Read the information that was given to you.

*February 14, 2017*

**math**

With 90 cattle, he has 9/4 as many mouths, so 4/9 as long to eat: about 16 days

*February 14, 2017*

**Pre calculus**

I cannot find a function of the form 80 + a*e^(-kx) which fits more than two of the points, since when x=0, you have 80+a=176, so a=96 and when x=1 you have 80+96e^-k = 169 e^-k = 89/96 k = ln(96/89) = 0.07571 80+96e^(-0.0757x) does not fit any of the other points.

*February 14, 2017*

**Math**

Each inch has 8 1/8-inch parts. So, 3 1/2 inches is 28 times as long. so, ... or, each inch represents 8 feet. so, 3.5 inches is ? feet

*February 14, 2017*

**Math**

terms are separated by + and - signs.

*February 14, 2017*

**math**

If you plug in your numbers here http://davidmlane.com/hyperstat/z_table.html You will see that it is the 87th %ile.

*February 14, 2017*

**Maths**

p+q = 150 3/4 p = 2/5 q I suspect a typo, as the solution is not an integer.

*February 14, 2017*

**Physical Science**

thank you

*February 14, 2017*

**Physical Science**

A delivery man pushes the button to ring the doorbell. Which of the following forms of energy is not involved in this process? electrical sound mechanical gravitational my answer is gravitational

*February 14, 2017*

**Geometry**

You have 4 sides. Add 'em up and subtract from 30 to get the 5th side. Now, how many are equal?

*February 14, 2017*

**Algebra**

a) which two factors of 6 add to 5? b) which two factors of 6 differ by 1? c) which two factors of 6 add to 1?

*February 14, 2017*

**Algebra**

even integers differ by 2, so the three numbers are x, x+2 and x+4. Now you are told that x(x+2) = 11(x+4)-8 Now solve for x.

*February 14, 2017*

**Math Calc**

the range for an angled shot is R = v^2/g sin2? so, plug in your numbers. Remember to convert ft/s to mi/hr.

*February 14, 2017*

**Math - Calculus**

Recall that the vertical height h is h(t) = 6 + (810 sin42)t - 16t^2 so, just solve for t when h=0.

*February 14, 2017*

**Algebra**

C = P if 0 < P <= 100 Now you can do the part where P > 100, right?

*February 14, 2017*

**Math**

No. That is only the numbers between 0 and 15. You are not restricted to positive values.

*February 14, 2017*

**Math**

real numbers that are less than 15 means s<15

*February 14, 2017*