Saturday
January 31, 2015

Posts by STEVE


Total # Posts: 28,511

Algebra 1
zero solutions. -3x+6y cannot equal both 10 and -4. The lines are parallel, and so, do not intersect.
December 18, 2014

Algebra 1
The first line should read -3x
December 18, 2014

Algebra 1
How many solutions does this system have? *3x + 6y = 10 -3x + 6y = -4
December 18, 2014

algebra 1
that is correct. If you dislike working with fractions, you can start over and eliminate y instead of x.
December 18, 2014

algebra 1
-16x-2y=-18 8x+y=9 Multiply the 2nd by 2 to get -16x-2y=-18 16x+2y = 18 These are the same line. There are infinitely many solutions. Any point on one line is also on the other, as the lines coincide.
December 18, 2014

physics
when you say constant velocity, that means zero acceleration.
December 18, 2014

Chemistry
(.0658*0.3)/(.015)
December 18, 2014

Math
count the deposits, and count the amounts: If there were x deposits at $5, and y at $3.50, then we know x+y=14 5x+3.50y=59.50 Now just plug and chug.
December 18, 2014

Chemistry
Since PV is constant, and you have increased the volume by a factor of 1000, the pressure is reduced by a factor of 1000.
December 18, 2014

math
Since the 54% and the 63% grades count as 80% of her grade (and assuming therefore that each counts as 40%), the final grade is (54+63)(0.4) + 80(.2) = 62.8
December 18, 2014

math
If they sell x tacos, the profit for the day is 3.25x - 210 So, set that > 0 and solve for x.
December 18, 2014

Math
correckit!
December 18, 2014

Math
if it is not included, then you subtract it from the total. So, ...
December 18, 2014

math algebra
Since y is the cost of a sandwich with x extra veggies, the y-intercept is the cost with 0 veggies. the two extra veggies (5-3) cost $1.00 more. So, the veggies are $0.50 each. That means 0 extra veggies (the y-intercept) must be at 5.25-1.50 = 3.75 Looks like (D) to me y = 0....
December 18, 2014

physic
well, torque = radius * force T = rF if the radius is doubled, the new torque is T' = (2r)F = 2rF = 2T
December 18, 2014

Physics
If he cleared the bar at the top of his swing, then all his speed was horizontal, at 10.2 m/s. All that stuff about mass and height is just noise. Trying to incorporate other forces is impossible without further data.
December 18, 2014

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

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