# Posts by STEVE

Total # Posts: 49,546

**Science**

20/(60+20) = 1/4

*February 20, 2017*

**Chemistry**

.28 * 6.023 * 10^23 * 2

*February 20, 2017*

**Algebra**

well, 2 days = 48 hours, so ...

*February 20, 2017*

**Calculus**

#1 swap variables and solve for y: x = ?(3y-2) x^2 = 3y-2 y = (x^2+2)/3 now f(x) has domain: x >= 2/3 range: y >= 0 f^-1(x) has domain: x >= 0 range: y >= 2/3 because f(x) has only one branch #2 f(x) = ?[1,x] sin(t)/t dt I don't think you want f(x), because it ...

*February 19, 2017*

**Math 104**

5P2 = ?

*February 19, 2017*

**math**

(2,3) [2,3]

*February 19, 2017*

**Algebra2**

write a recursive formula for the sequence 5,18,31,44,57 then find the next term. My answer is a1=5,an=an-1+13 The next term would be 70.

*February 19, 2017*

**Calculus II**

google the topic and you will find many discussions and examples. For a region of uniform density, the center of mass is the same as the centroid.

*February 19, 2017*

**Pre-Calculus**

3 = 2.1 sin[(?/6)t - 5?/6] + 3.2 2.1 sin[(?/6)t - 5?/6] = -0.2 sin[(?/6)t - 5?/6] = -0.095238 (?/6)t - 5?/6 = -.0953826 (?/6)t = 2.522611 t = 4.8178 and of course, there is another solution

*February 19, 2017*

**Math**

9.50a + 5.50(148-a) = 1170.00

*February 19, 2017*

**Algebra2**

thank you

*February 19, 2017*

**Algebra2**

cd = k a constant. So, you want d such that 86d = 2*17

*February 19, 2017*

**Algebra2**

suppose c and d vary inversely and d=2 when c=17 write an equation that models that variation find d when c=68

*February 19, 2017*

**Algebra2**

note that xy = 10

*February 19, 2017*

**Algebra2**

Does the relation in the table represent direct variation, inverse variation, or neither? if it is direct or inverse variation, write an equation to represent the situation. Explain your answer x 5, 10, 15, 20 Y 2, 1, 2/3, 1/2

*February 19, 2017*

**MATH**

15/(10+15) = 3/5 = 60%

*February 19, 2017*

**Maths bearing**

use the law of cosines.

*February 19, 2017*

**Math**

use the law of cosines.

*February 19, 2017*

**Math**

I'd guess the same, if it's in the same circle ...

*February 19, 2017*

**Differential equation**

?? Just plug in the numbers: at r=3, dr/dt = 5?/36 = k/9 k = 5?/4

*February 19, 2017*

**Math**

since 1 revolution is 360 degrees, (25 * 2? ft/rev) * (2?/10 rev/s) * 3600s/hr * 1mi/5280 ft = 10.71 mi/hr

*February 19, 2017*

**Math**

looks like it already is!

*February 19, 2017*

**math**

subtract the area of the lawn from the total area including path: (50+16)(40+16)-50*40 = ?

*February 19, 2017*

**fractionss**

2/3 * 1/2 ordered dessert

*February 19, 2017*

**fractions**

the amount left was (1 - 4/7)(1 - 2/5) = 3/7 * 3/5 = 9/35 of the original amount. So, 9/35 x = 9 x = 35

*February 19, 2017*

**Differential equations**

yes indeed

*February 19, 2017*

**Maths**

3*2*(120+68) = 1128m

*February 19, 2017*

**math**

read this and follow the example. What do you get? Hint: the curve looks like a straight line to me ...

*February 18, 2017*

**Math**

hard to say, with no diagram and no description...

*February 18, 2017*

**Math**

.60*70 + x*40 = .70*110 x = .875 so, they must win 7/8 * 40 = 35 of the remaining games. Good luck with that...

*February 18, 2017*

**math**

x=1, so A=1+2+1 = 4 ...

*February 18, 2017*

**Math**

-1/8 (x+35)= -7 x+35 = -7(-8) = 56 x = 21

*February 18, 2017*

**calculus**

E = IR dE/dt = R dI/dt + I dR/dt If E is constant, then dE/dt = 0 if R=20, then I = 5, so you can use that in the formula above. Naturally, if R is increasing, the current is decreasing.

*February 18, 2017*

**physics**

geez - you have the equation - plug in the numbers.

*February 18, 2017*

**math**

D is the lateral area. If you include the base, then you get choice B

*February 18, 2017*

**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*