Tuesday

February 21, 2017
Total # Posts: 48,686

**Math**

10000*0.10*n = 5000 or, each year's interest is $1000, so ...

*December 27, 2016*

**Math**

j = t-5 jt = 126 Hint: 9*14 = 126

*December 27, 2016*

**Math - typo?**

you sure that h(2) = 44? I suspect it is h(3) = 44.

*December 27, 2016*

**Maths - Cartesian Equations**

(y/2)^2 = (t + 1/t)^2 = t^2+2+1/t^2 x^2 = (t - 1/t)^2 = t^2-2+1/t^2 y^2/4 - x^2 = 4 or in standard form, y^2/16 - x^2/4 = 1

*December 27, 2016*

**Maths - Parametric Equations**

(a) surely you can just plug in a value for t! x = 2cos(8?/3) = 2(-1/2) = -1 y = 2sin(8?/3) = 2(?3/2) = ?3 (b) Now you have a point and a slope, so the tangent line is y-?3 = 1/?3 (x+1)

*December 27, 2016*

**Maths**

5x * 2x = 360 Find x, and then you know the base and height.

*December 27, 2016*

**Math**

If there are x tables, then we have 9(x-2) = 6x+3

*December 27, 2016*

**Math**

just consult a map. I mean, there aren't that many oceans, right?

*December 27, 2016*

**value**

misspelled

*December 27, 2016*

**social stadies**

misspelled

*December 27, 2016*

**economics**

Note that the marginal cost is the derivative of the total cost. Note that the average variable cost is the integral of the marginal cost over the given interval. AVC is a minimum when MC = AVC. A nice video is here: https://www.youtube.com/watch?v=TBCAHbhhvTg

*December 27, 2016*

**calculus help me plz too hard show step**

R dQ/dt + Q/C = 0 R dQ/dt = -Q/C dQ/dt = -Q/(RC) dQ/Q = -1/(RC) dt lnQ = -1/(RC) t + k at t=0, we know that Q=Qo, so lnQo = k so, lnQ = -1/(RC) + lnQo ln(Q/Qo) = -1/(RC) t Q/Qo = e^(-t/RC) Q = Qo e^(-t/RC)

*December 27, 2016*

**Math**

x^2 = ln(xy) x^2 = lnx + lny 2x = 1/x + 1/y y' y' = y(2x - 1/x) y'(1) = e(2-1) = e or, more explicitly, ln(xy) = x^2 xy = e^(x^2) y = e^(x^2)/x y' = e^(x^2) (2x-1)/x^2 y'(1) = e^1 (2-1)/1 = e

*December 27, 2016*

**math**

first step: STOP REPEATING THE POST!

*December 26, 2016*

**math**

surely you can do 3*5 now just move the decimal point as needed. .5% = 1/200 I'm sure you can do 3200/200 .5 is 1/2, but .5% is not. 10.00 - 8*0.82 = ?

*December 26, 2016*

**algebra**

http://www.wolframalpha.com/input/?i=plot+y%3C%3D+3%2F2+x%2B3,+2x+%2B+y%3C10,+y%3E-1

*December 26, 2016*

**Proofing Maths**

of course. |x-y| = |x + (-y)| <= |x| + |-y|

*December 26, 2016*

**Physics**

7@N40W = <-4.50,5.36> 10@E = <10.00,0.00> now just add them up and use the normal distance formula.

*December 26, 2016*

**algebra**

They are the same equation, so infinitely many solutions.

*December 26, 2016*

**Math**

h'(1) = f'(f(1)) f'(1) = f'(3)f'(1) = 7*2 = 14

*December 26, 2016*

**algebra**

256z^2 -4 -192z^2 +3 = (256z^2-4) - 3(64z^2-1) = (16z-2)(16z+2)-3(8z-1)(8z+1) = 4(8z-1)(8z+1)-3(8z-1)(8z+1) = (8z-1)(8z+1) cool, eh?

*December 26, 2016*

**Maths(Surface integral/flux)**

recall polar coordinates: x^2+y^2 = r^2 dx dy = r dr d?

*December 26, 2016*

**calculus too hard**

just keep on ... dx/dt = k(a-x) dx/(a-x) = kt ln(a-x) = kt^2/2 or, using a new k ln(a-x) = kt^2 a-x = e^(kt^2) Now use your initial conditions to find a and k.

*December 26, 2016*

**math**

or, see how much 1 set of 9 notes is worth: 2*3+5*2+10*4 = 56 728/56 = 13 So there are 13 sets of 9 notes...

*December 26, 2016*

**math**

Add up the value of each kind of note: 2(3x)+5(2x)+10(4x) = 728 now find x, and the total number of notes is 3x+2x+4x = 9x

*December 26, 2016*

**ACCOUNTING**

<font Courier/> hello

*December 26, 2016*

**ACCOUNTING**

p { font-family: "Times New Roman", Times, serif; } Times Roman

*December 26, 2016*

**ACCOUNTING**

???? ???? ???? ???? ? ?? ? ?? ? ?? ? ?? ???? ???? ???? ???? ???? ???? ???? ???? ????????????????????? ? ????? Some Text ?? ? ????? in the box ?? ?????????????????????? ? ??????? ?? ? ??????? ?? ?????????????????????? ?????????????????????

*December 26, 2016*

**ACCOUNTING**

???? ???? ???? ???? ? ?? ? ?? ? ?? ? ?? ???? ???? ???? ???? ???? ???? ???? ???? ????????????????????? ? ????? Some Text ?? ? ????? in the box ?? ?????????????????????? ? ??????? ?? ? ??????? ?? ?????????????????????? ?????????????????????

*December 26, 2016*

**MATH**

recall that log and ^ are inverse operations: 10^(log x) = x log(10^x) = x so, now you can do 10^(log_10(a)) = 10^4 a = 10^4

*December 26, 2016*

**Math**

y-x = 4 3x = 2y+4

*December 26, 2016*

**Proofing Maths**

google is your friend. Lots of help with the triangle inequality. Once you have convinced yourself that |x+y| <= |x| + |y| then it is a simple extension to get to your problem.

*December 26, 2016*

**Math**

since tests count twice, add them twice. The total points must be the same as 5 scores of 70: 88+82+84+2x = 70*5 x = 48

*December 26, 2016*

**MATHS**

minar?

*December 26, 2016*

**physic**

If you mean a point on the edge of the wheel, then recall the relationship between linear speed v and angular speed ?: v = r? since arc length s = r?

*December 26, 2016*

**science**

Since the weight is proportional to 1/r^2, 5 times the weight means 1/?5 times the distance.

*December 26, 2016*

**Math**

The trick here is to recall that 1 = cos^a+sin^2A cos2A/(1+sin2A) (cos^2A-sin^2A)/(1+2sinAcosA) (cos^2A-sin^2A)/(cos^2A+2sinAcosA+sin^2A) (cosA+sinA)(cosA-sinA)/(cosA+sinA)^2 (cosA-sinA)/(cosA+sinA) (cotA-1)/(cotA+1)

*December 26, 2016*

**Math**

when you post something, bring it up so you can see what actually made it.

*December 25, 2016*

**Math**

better try again.

*December 25, 2016*

**Math**

nope. -8-2 = -10

*December 25, 2016*

**Math**

Nope. -8(2) + 5 = -16 + 5 = -11

*December 25, 2016*

**Math**

not complicated at all. Any group of n repeating digits (.ddd) can be represented by ddd/999 where there are as many 9's as digits. So, 0.583 = 583/999 To see why this is so, consider what happens if you assign the value to a variable, say x: x = 0.583583583... Now, shift ...

*December 25, 2016*

**math-integrating factor**

well, did you try it? d/dx (y/x) = 1/x y' - y/x^2 so, now you have an exact differential, which is what you wanted.

*December 25, 2016*

**Functions**

when after x months, .15x = 9.25

*December 25, 2016*

**mathes**

since a=25 and b=20, the ellipse can be represented by x^2/25^2 + y^2/20^2 = 1 Now just find 2x when y=10.

*December 25, 2016*

**Math**

let u = cotx. Now the integrand is just -u^4 du

*December 25, 2016*

**Math**

RT = 2.5 tan40° RQ = 2.5 tan65° so, tan <RQT = RT/RQ

*December 25, 2016*

**mathematics**

hint: find the center, then a=2 b=3 c^2 = a^2-b^2

*December 24, 2016*

**A.p.**

come on, guy. Algebra I here.

*December 24, 2016*

**a.p.**

1st 100 ft = 250 then .25(x-100)

*December 24, 2016*

**ellipse - ahem**

b^2+c^2 = a^2

*December 24, 2016*

**algebra**

well, did you try your solution to see whether it works? 3(-5)-(-6) = -15+6 = -9 4(-5)-(-6) = -20+6 = -14 Clearly not. SO, what happened? Using the first equation, we see that y = 3x+9 Using that in the other equation, we get 4x-(3x+9) = -4 4x-3x-9 = -4 x = 5 So, y = 3x+9 = 15...

*December 24, 2016*

**mathematics**

what, you can't plug in the numbers? 1/f = 1/(7/2) - 1/(15/2) 1/f = 2/7 - 2/15 1/f = (30-14)/105 1/f = 16/105 f = 105/16

*December 23, 2016*

**maths 10-3**

(3 ft 2 1/2 in)/2 = (3/2 ft)+(1 1/4 in) = 1 ft 6 in + 1 1/4 in = 1 ft 7 1/4 in

*December 23, 2016*

**algebra**

(t+2v)(t+2v) (z-3)(z+14)

*December 23, 2016*

**math**

just plug into your formula for volume: v = 4/3 * 3.14 * 10^3 = ?

*December 23, 2016*

**Math**

51 = .85x

*December 23, 2016*

**Alegebra**

dilation relative to (0,0) just means you multiply all the coordinates by the dilation factor. You are increasing all the distance from the origin by the scale factor. For example, with a scale factor of 3, (2,-12)->(6,-36) With a scale factor of 1/4, (-12,8)->(-3,2)

*December 23, 2016*

**physics**

maximum range is when the angle is 45° so, minimum velocity need for a given range is at 45° Now just use your range formula using 45° to see what initial velocity has that range. That is your minimum required velocity. Technically, a 1000km range has to include ...

*December 23, 2016*

**Algebra**

y = x+13 y = 2x+5 Looks like x=8 and y=21

*December 23, 2016*

**value**

since distance = speed * time, we need at time t hours 60t = 5(t - 1/3)^2 note: 10 km/hr is speed, not acceleration. I used a = 10 km/hr^2

*December 23, 2016*

**maths**

C is 1/4 of the way from A to B. So, add 1/4 of the difference in coordinates (B-A) to A: C = (-18,8)+(2,-4) = (-16,4)

*December 23, 2016*

**Maths**

The line has slope 3/4 So, the radius has slope -4/3 Thus, the line with that slope through P is y-4 = -4/3 (x+3)

*December 23, 2016*

**Maths**

Suppose the slopes are equal: -k/(k+1) = -4/(3k) -3k^2 = -4k-4 3k^2-4k-4 = 0 (3k+2)(k-2) = 0 k = 2 or -2/3 as you calculated. Using you pairs of equations, we see that they can be written 4x+6y=16 4x+6y=4 2x-y = -24 2x-y = 2 In both cases the lines are distinct and parallel, ...

*December 23, 2016*

**Pre-calc Math**

Draw a diagram. T = top of tree S = tip of shadow B = base of tree Draw a line L horizontally from the tip of the shadow. Drop a vertical from the tree base to intersect line L at P. Let x = SP y = PB h = BT (height of tree) y = 210 sin21° x^2+y^2 = 210^2 (y+h)/x = tan51&...

*December 23, 2016*

**Pre-calc Math**

Draw a diagram. If the height is h, h cot84° - h cot87° = 95 (a) the distance d is found via h^2+(h cot87°)^2 = d^2

*December 23, 2016*

**Pre-calc Math**

sinB/109 = sin24°/78 That gives you B Then C = 180-(A+B) then c/sinC = a/sinA

*December 23, 2016*

**Algebra**

just use the quadratic formula: x = (2a±?(4a^2+16a))/(2a) = (2a±2?(a^2+4a))/(2a) = 1±?(a^2+4a)/a or = 1±?(1 + 4/a)

*December 23, 2016*

**Transformations**

stretch = dilation shift = translation there is no reflection involved. It amazes me that you could not figure that out. I assume you know that x is horizontal and y is vertical...

*December 23, 2016*

**Transformations**

y = 4(2(x-3/2))^2+1 shift right 3/2 horizontal shrink by 2 vertical stretch by 4 shift up 1 or y=16(x-3/2)^2+1 shift right 3/2 vertical stretch by 16 shift up 1

*December 23, 2016*

**SAT Math**

m% of 50 is m/100 * 50 = m/2 20% of n is 20/100 n = n/5 m/2 = n/5 m/n = 2/5 check: m=50, n=125 50% of 50 = 25 20% of 125 = 25 m/n = 2/5

*December 23, 2016*

**math**

3(2tanA)/(1-tan^2A) = 2tanA+1 Now just solve for tanA

*December 22, 2016*

**Grade 6 Maths**

Looks like 7n+1

*December 22, 2016*

**SAT Math Question?**

p-q is largest if p is big and q is small: p-q <= 30-7 = 23 similarly, p-q >= 15-19 = -4

*December 22, 2016*

**Maths - Linear Relations Simple Problem**

if the line intersects, then we have (x-1)^2+5 = mx+2 x^2-2x+6 = mx+2 x^2-(m+2)x+4 = 0 For no solutions, you must have the discriminant negative: (m+2)^2 - 16 < 0 ...

*December 22, 2016*

**math**

z = (148-x-y)^2 x+?y + (148-x-y)^2 = 82 ?x+y + (148-x-y)^2 = 98 now you have just two equations in x and y. Or, assume integer solutions. Then x,y,z must all be perfect squares. Looking at the sums, it should be clear that y>x>z. Now just try a few small numbers. Let z=9...

*December 22, 2016*

**Physical Science**

the equation says that 2 moles of Na react with 1 mole of Cl2 4/2 = 2, so just multiply all the quantities by 2: 4 moles Na react with 2 moles Cl2.

*December 22, 2016*

**Specialist Mathematics**

google "triangle inequality" for many discussions and proofs

*December 22, 2016*

**Algebra 1**

the 3" frame is on both sides, so you need x^2 - (x-6)^2 = 12x-36

*December 22, 2016*

**physics**

his acceleration is 4m/s^2 F = ma 1/10 the time means 10 times the acceleration.

*December 22, 2016*

**co-ordinate geometry**

the locus is a parabola, as you can see from the definitions of the parabola. The directrix is the line x=0. Use what you know about the equation y^2 = 4px In this case, the focus is at (4,0), so the vertex has been shifted to (2,0) and the equation is y^2 = 4p(x-2) Now figure...

*December 22, 2016*

**science**

C=12 O=16 so, ...

*December 22, 2016*

**math**

tan(atan(2/3)-atan(2/5)) = (2/3 - 2/5)/(1+(2/3)(2/5)) = 4/19 = 0.21 as above

*December 22, 2016*

**math**

The figure is a rectangle, since 15^2 + 20^2 = 25^2 The area is thus 15*20 = 300

*December 22, 2016*

**Maths**

27 = s^3

*December 22, 2016*

**math**

see related questions below.

*December 22, 2016*

**MATH**

If he uses x liters of 20%, then the rest (80-x) must be 60%. Now just look at the amounts of acid present: .20x + .60(80-x) = .30*80

*December 22, 2016*

**Calculus**

You are correct.

*December 22, 2016*

**Maths**

x+100 = 3x+50

*December 21, 2016*

**a.p.**

Surely by now you have some idea how to write the words in algebra. If last year's certificate was worth Rs a, then ar = a + 100 ar^12 = 7200 Now go to work on that.

*December 21, 2016*

**g.p.**

clearly a geometric series. What do you know about them?

*December 21, 2016*

**Physics**

it rose vertically 5/2 meters, so ...

*December 21, 2016*

**Algebra 1**

Since the 18" pizza has 3 times the diameter of the 6" pizza, it has 9 times the area. You'd have to buy 9 small ones to get the same amount of pizza as a large one. so, ...

*December 21, 2016*

**math**

1000(1+.063/12)^19

*December 21, 2016*

**a.p.**

pair them up. (1-2)+(3-4)+... That's basically just n/2 * -1 depending on n even or odd.

*December 21, 2016*

**a.p.**

Sn = n/2 (2*2+(n-1)*3) > 200

*December 21, 2016*

**a.p.**

just add up the two series 2+5+8+...+(3n-1) 3+6+9+...+3n those are easy, right?

*December 21, 2016*

**math**

Huh? The original polynomial? You want (5x^2-3x-9)-(5x^2-3x-9) = 0 now just change the signs of the 2nd polynomial so you can add it instead of subtracting.

*December 21, 2016*

**math**

well, 5 + -5 = 0 -3 + 3 = 0 ...

*December 21, 2016*