Thursday
February 23, 2017

Posts by steve

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
47
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
321
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

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