Friday

January 30, 2015

January 30, 2015

Total # Posts: 28,495

**Physics**

speed s is found by conserving momentum: 800s = 3*10 time = 6.4/s
*December 18, 2014*

**math**

d/dr (r^3) = 3r^2 It's just the normal power formula So, dV/dr = (4/3)pi (3r^2) dV = 4pi r^2 dr Don't lose track of the dr when doing related rates
*December 18, 2014*

**Math**

well, dy = -1 / 2√(7-x) dx So, just plug in your numbers
*December 18, 2014*

**algebra**

you need an equation for the number of plays and the points for them: x+y = 21 3x+y = 49
*December 18, 2014*

**math**

The price p for e eggs is p/e = 1/6
*December 18, 2014*

**Math**

well, just compare the two plans for how much it costs the patient: 400 + 0.35(x-400) > 1000 + 0.25(x-1000)
*December 18, 2014*

**math**

.85p = 76
*December 18, 2014*

**Math- algebra**

well, you want y when x = -b/2a = 26/32 google will evaluate many algebraic expressions. Just type it into the search box.
*December 17, 2014*

**math**

15/x = cos 60°
*December 17, 2014*

**math**

clearly, 23.25/3 or 7.75
*December 17, 2014*

**math**

well write the ratios and see which are the same when reduced to lowest terms. For example 6/3 and 20/10 are the same ratio
*December 17, 2014*

**Algebra 1**

Describe how the graphs of y = absolute x and y = absolute x +2 are related.
*December 17, 2014*

**Calculus**

since f'(x) = -1 which is never zero, there are no relative min or max points. So, the extrema will just be the values at the endpoints of the interval. So, just find f(-1) and f(2). I mean, don't forget your Algebra I just 'cause you're in calculus now. f(x) ...
*December 17, 2014*

**math**

25q+5n+10d = 4500 q = 5n n = 3d So, start substituting and the values will become clear.
*December 17, 2014*

**AP AB Calculus**

(c),(d) just plug in 4.2 for x and solve for y. That will be the value for k. Since (d) will be a cubic in y, it might take a graphical solution.
*December 17, 2014*

**Algebra 1**

Write the equation of a line that is perpendicular to the given line and that passes through the given point. y-3 = 8/3 (x+2); (-2,3)
*December 17, 2014*

**Math**

u^-3 = 1/125 u^-3 = 5^-3 u = 5 y-1 = 4y - 2/3 3y-3 = 12y-2 9y = -1 y = -1/9 The y-intercept is where x=0. Clearly when x=0, y = -5, not 5. If she ran x miles, then we know that x+40 = 10+4x x = 10 If you want the slope, try writing the equation is slope-intercept form: 4x-6y+...
*December 17, 2014*

**Algebra**

I'd do C
*December 17, 2014*

**Algebra 1**

just change the slope to -1/(8/3)
*December 17, 2014*

**Algebra 1**

Write the equation of a line that is perpendicular to the given line and that passes through the given point. y-3 = 8/3(x+2); (-2,3)
*December 17, 2014*

**Math! 2 question! Need help!**

why not just review your point-slope form? The line passing through (h,k) with slope m is y-k = m(x-h) Now just plug in your values.
*December 17, 2014*

**calculus honor**

hey, honor student -- find what when x=1?
*December 17, 2014*

**calculus**

v = pi r^2 h dv/dt = pi r^2 dh/dt
*December 17, 2014*

**calculus**

a = pi r^2 da/dr = 2pi r
*December 17, 2014*

**Math( Can you help me with starting this problem)**

hmm. They gave you the formula, so just use it: v = 4/3 pi r^3 dv/dt = 4pi r^2 dr/dt So, just solve for dr/dt
*December 17, 2014*

**caculus**

If the base of the ladder is x from the wall, and the top of the ladder is y high, then x^2+y^2 = 10^2 x dx/dt + y dy/dt = 0 So, figure y when x=6 and just plug in the numbers to find dy/dt.
*December 17, 2014*

**Algebra**

so, plug in the numbers. solve for t when h=84 and 0
*December 17, 2014*

**math**

(2.6)(2.2)x10^(-4+8) = 5.72 x 10^4
*December 17, 2014*

**Algebra 1**

Tell whether them lines, for each pair of equations are parallel, perpendicular, or neither. y= -1/4x +10 -2x+8y=6
*December 17, 2014*

**math**

the three sizes clearly have different constants. For n dozen eggs, For the one-dozen size, p = 2(6.00n) For the half-dozen size, p = 2.18n For the 1 1/2-dozen size, p = (2/3)(3.00n)
*December 17, 2014*

**Algebra 1**

thank you
*December 17, 2014*

**Algebra 1**

Tell whether the lines for each pair of equations mare parallel, perpendicular, or neither. y= -2x+4 -5x+10y=5
*December 17, 2014*

**math**

My answers: 1. B 2. C 3. C 4. A
*December 17, 2014*

**Algebra 1**

Write an equation for the line that is parallel to the given line that passes through the given point. y=3x+7; (2,10)
*December 17, 2014*

**math**

I assume you mean leveling the ground for the roads. 3(225*5 + 175*5) = ? This assumes that the intersection is leveled twice.
*December 17, 2014*

**Algebra**

just factor y to get y = x(85-16x) So, what is x when y=0 (that is, when it hits the ground)?
*December 17, 2014*

**Algebra II**

If there are x price decreases, then price = 6.00 - .25x or 6-x/4 demand = 330 + 15x Since revenue = price * quantity, r(x) = (6-x/4)(330+15x) = -15/4 x^2 + 15/2 x + 1980 Now use what you know about parabolas to find the vertex. Since this parabola opens downward, the vertex ...
*December 17, 2014*

**Math**

If side x is parallel to the river, xy=1800 The perimeter is p = 2(x+y) = 2(x + 1800/x) p is a max when 1 - 1800/x^2 = 0, or x = 30√2 So, the field is 30√2 by 30√2 As usual, maximum area (or minimum perimeter) is achieved by a square.
*December 17, 2014*

**Maths**

h = 2g 2h+4g+h+g = 99 So, 11g = 99 g=9 9 goats and 18 hens
*December 17, 2014*

**Mathematics**

the first thing I'd do is divide by 20E6 and get 2/x - 3/(.5-x) = 0 2/x = 3/(.5-x) 2(.5-x) = 3x 1 - 2x = 3x x = .2
*December 17, 2014*

**Math**

amplitude = (8-5)/2 period = (5π-3π)*2 = 4π Assuming the cited min and max are consecutive extrema (that is, half the cycle)
*December 16, 2014*

**Algebra**

(3x+4)^5 = 4^15 = (4^3)^5 So, 3x+4 = 4^3 = 64 x = 20 That's the only solution I see.
*December 16, 2014*

**Algebra 1**

Write y= -2/3x +7 in standard form using integers.
*December 16, 2014*

**Calculus**

Hmmm. As I recall, the average value of f(x) on [a,b] is ∫[a,b] f(x) dx ------------------ b-a e^(4x^2) is an even function, so its average value cannot be zero over [-1/4,1/4]. ∫[-1/4,1/4] e^(4x^2) dx Unfortunately, ∫e^(x^2) dx is not an elementary integral.
*December 16, 2014*

**Algebra 1**

thank you
*December 16, 2014*

**Algebra 1**

Write an equation in point slope form for the line through the given point with the given slope. (4,-7); m= -0.54
*December 16, 2014*

**calculus**

no, s(t) is the position function. You want the velocity, which is ds/dt = -9.8t then you can sub in t=3. And, since the ball is falling, s(t) = -4.9t^2 + 550
*December 16, 2014*

**Trig/Precalc**

Yes, there are lots of such formulas. One is at http://www.uwfox.uwc.edu/users/tnyman/TRIGConcepts/Asinx+Bcosx.pdf where you will see that the amplitude of your function is √(5^2+6^2) = √61
*December 16, 2014*

**Algebra 2**

ax+by=c ax=c-by x = (c-by)/a
*December 16, 2014*

**math**

Mr jacob is 55 years old and Tony is 7 years old. In how many years will Mr. Jacob be 4 times as old as Tony?
*December 16, 2014*

**math**

The cost of 5 similar digital cameras and 3 similar video cameras is $3213. each video camera costs 4 times as much as each digital camera. John buys a digital camera and a video camera. How much does he pay?
*December 16, 2014*

**math**

Three times as many children as adults attended a concert on Saturday. An adult's ticket cost $7 and child's ticket cost $3. the theater collected a total of $6,000. How many people bought tickets?
*December 16, 2014*

**English - Writeteacher**

Your choices look good to me.
*December 16, 2014*

**math**

(4/56)*42 Or, you can write that as x/42 = 4/56
*December 16, 2014*

**Chemistry**

I think that the crystal lattice has little to do with it at this point. By saying that the Al atom has a volume, they just want you to divide the mass of an atom by its volume. Without more information on the lattice spacings in 3D, it's hard to say how much space an atom...
*December 16, 2014*

**MATH**

1/(6 4/5) * 30
*December 16, 2014*

**Math One question! Help!**

The rate of change is the slope of the line. The slope-intercept form of this line is y = -5/3 x - 2/3
*December 16, 2014*

**Algebra 2**

to evaluate c, just plug in x(t) wherever there's an x: c(x(t)) = 60x(t)+750 = 60(50t)+750 = 3000t+750 Now just plug in t=5 to get c(x(5)).
*December 16, 2014*

**English**

Looks to me like STAY is intransitive ASKED is transitive, since it has an object.
*December 16, 2014*

**physics**

v = at where a is just the acceleration due to gravity. So, solve for t in 9.8t = 85(1000/3600)
*December 16, 2014*

**Math**

wherever you see an x, place a -7. So, f(-7) = -(-7)-6 = 7-6 = 1
*December 16, 2014*

**Math**

well, there's 1* log + 1/2 * log Looks like 3/2 * log to me... Do you have trouble with x + 1/2 x = 3/2 x?
*December 16, 2014*

**Math**

2 = (1/2)^-1, so log(1/2)2 = -1 log(1/2)2 + log(1/2)2^(1/2) log(1/2)2 + (1/2)*log(1/2)2 (3/2)*log(1/2)2 (3/2)(-1) -3/2
*December 16, 2014*

**calculus**

If the base of the ladder is x away from the wall, and the top of the ladder is at height y, then x^2+y^2 = 25^2 x dx/dt + y dy/dt = 0 So, figure y when x=20, and plug in dx/dt=0.18 to find dy/dt.
*December 16, 2014*

**Math**

reflection over the x-axis takes (x,y) -> (x,-y) So, just change the sign of all the y-coordinates in your points.
*December 16, 2014*

**algebra**

The fundamental theorem of algebra says that every polynomial of degree n has exactly n roots. So, look at the highest power of the variable.
*December 16, 2014*

**maths**

99... still working on the ending digit(s)
*December 16, 2014*

**MATH**

The answer is clearly 5, because you have to include the 3 the person ate!
*December 16, 2014*

**Math**

just google it. You will find many proofs of it.
*December 16, 2014*

**Math - incomplete**

how many partitions? Is the fence used to separate the partitions? And what do you want x to represent?
*December 16, 2014*

**math**

You need to divide the region into two parts at x=1, where 3x and 5-2x intersect. a = ∫[0,1] (3x - x/2) dx + ∫[1,2] (5-2x - x/2) dx See the region at http://www.wolframalpha.com/input/?i=plot+y%3D3x%2Cy%3Dx%2F2%2Cy%3D5-2x
*December 16, 2014*

**math**

s = ∫[0,5] √(1+y'^2) dx = ∫[0,5] √(1+9x/4) dx That will give the length of one branch of the curve.
*December 16, 2014*

**chem**

NaH2PO4 Molecular Weight 119.98 I guess that's about as close as you're gonna get. But I guess you can use google as well as I can...
*December 16, 2014*

**MATHS**

n = 2d-4 (n+1)/(d+1) = 3/2 (2d-4+1)/(d+1) = 3/2 2(2d-3) = 3(d+1) 4d-6 = 3d+3 d = 9 So, the original fraction is 14/9
*December 16, 2014*

**Chemistry**

Hmmm. Which of those devices do you know has an antenna?
*December 16, 2014*

**basic chemistry**

you need the balanced equation: 2Na3PO4 + 3BaCl2 --> Ba3(PO4)2 + 6NaCl So, each 2 moles of Na3PO4 yields 1 mole of Ba3(PO4)2
*December 15, 2014*

**Physics**

clearly, since they are all on the same rigid platform, their rotational periods are all the same. Since the circumference is just a constant times the radius, their speeds are in the same proportion as their radii. Someone 1/2 as far out is going 1/2 as fast. since the radial...
*December 15, 2014*

**Algebra 3**

you just need to remember that the vertex of the parabola y = ax^2+bx+c occurs at x = -b/2a.
*December 15, 2014*

**pre algebra**

You are correct as far as you got. By the time the police get started, the robbers are 13 miles ahead. The police are going 60 mi/hr faster than the crooks. So, you can think of the problem as the same thing as the robbers are standing still 13 miles ahead, and the police are ...
*December 15, 2014*

**Calculus**

if you let u = 1 + (x-3)^2 then y = 1/u The chain rule says that y' = -1/u^2 u' = -1/(1+(x-3)^2)^2 * (2(x-3))
*December 15, 2014*

**Algebra 1**

Thank you
*December 15, 2014*

**Algebra 1**

what is the equation to y= -1/12x+4 so that the 2nd line is parallel?
*December 15, 2014*

**Quick math help**

can't you see how incomplete your explanation is? Read that paragraph to anyone not familiar with the diagrams and they will blankly say, "Huh? what triangles?"
*December 15, 2014*

**math**

If the boat's speed is b and the current's speed is c, then since distance = speed * time, 10(b+c) = 210 70(b-c) = 210 Now just solve for b and s.
*December 15, 2014*

**Math**

a1+...+a9 = 5a + (0+2+4+6+8)d a2+...+a10 = 5a + (1+3+5+7+9)d so, 5a+20d = 17 5a+25d = 15 d = -2/5 a = 5
*December 15, 2014*

**Math Plz dont ignore Plz**

You just need to read through the words and write down the mathematical facts. They want to know how many adults and children were admitted. So, let's say there are a adults and c children. 1850 adults and children means a+c = 1850 $4.50 per child and $7.50 per adult and ...
*December 15, 2014*

**AP Calc BC**

y' = √x / -3y -3y dy = √x dx -3/2 y^2 = 2/3 x^(3/2) + c so, yes, you are correct y^2 = -4/9 x^(3/2) + c Not much to do with that. I guess you could use a new c. Name the old one k and you have y^2 = k - 4/9 x^(3/2) If k = 4/9 c then y^2 = 4/9 c - 4/9 x^(3/2) y...
*December 15, 2014*

**AP Calc B/C**

So, add up all the little wafers with diameter x^3, perpendicular to the x-y plane. They would have their centers at (x,y/2) with radius y/2 = x^3/2. The volume of a small semi-circular wafer of radius r and thickness dx is 1/2 πr^2 dx v = ∫[0,4] 1/2 π(x^3/2)^2...
*December 15, 2014*

**math**

well, since 27 = 4*6 + 3 what do you think?
*December 15, 2014*

**Math**

1/3 + √3/12 + 1/16 + √3/64 Using a common denominator of 64*3, we have (64 + 16√3 + 12 + 3√3)/192 (76+19√3)/192 or 19(4+√3)/192
*December 15, 2014*

**MATH**

-1+6 = 5, so -5(5) = ?
*December 15, 2014*

**math**

B:H = 4:7 H:J = 3:5 7*3 = 21, so we also have B:H = 12:21 H:J = 21:35 So, B:H:J = 12:21:35 12+21+35 = 68 136/68 = 2, so double everything so the sum is 136 B:H:J = 24:42:70 and those are the amounts for each girl.
*December 15, 2014*

**Algebra 1**

10.5^2
*December 15, 2014*

**Algebra 1 thx**

Does the coach count as one round? If so, the nth round has 3^n calls. If not, then the nth round has 3*3^n calls
*December 15, 2014*

**Algebra please help answer**

40/10 = 4, so it will triple 4 times. 3^4 = 81
*December 15, 2014*

**math**

If the cost is the same for x hours, then clearly 200+30x = 240+25x
*December 15, 2014*

**calc**

the tangent vector is ∇v = (dx/dt,dy/dt,dz/dt) ∇v = <4∛t,6t,-4/t^3> v(-1) = <3,-3,2>, so ∇v = <-4,6,4> Note that <-2,3,2> is parallel to ∇v(-1)
*December 15, 2014*

**math**

x=175, if that's what you are after
*December 15, 2014*

**Math**

since the ratio of the sides remains the same, x/5 = 5.1/3
*December 15, 2014*

**CAL**

y = 4/9 sinx - 1 y' = 4/9 cosx So, the slope of the tangent at x is 4/9 cosx The slope of the normal there is -1/y' = -1/(4/9 cosx) = -9/4 secx
*December 15, 2014*

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