Saturday
December 20, 2014

Posts by steve


Total # Posts: 27,640

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

Math
5000-7 = 4993 4993 = 5*998 + 3 7+4990 = 4997 The next number would have been 5002 Or, using modulo 5 math, 7 = 2(mod 5) 5000 = 0(mod 5) So, 5002 = 2 (mod 5)
December 15, 2014

Math
If the sequences are P and T, and their differences are Pd and Td, then T1 = -P1 2013/2 (2T1+2012Td) = 2013/2 (2P1 + 2012Pd) or, 2013P1 + 2025078Pd = 2013T1 + 2025078Td 4026P1 + 2025078(Pd-Td) = 0 We know that since T1 < 0 and the sum of T is the same as the sum of P, that ...
December 15, 2014

calculus
There must be problems on extrema. The extrema occur where f' = 0. Here, f(x) = x^(1/3) f'(x) = 1/3 x^(-2/3) f'(x) is never zero anywhere, especially in this interval. So, we just want the maximum and minimum values attained on the interval. Note that f' > 0...
December 15, 2014

Algebra 1
What is an equation of the line with slope 6 and y intercept -4?
December 15, 2014

Math
For all the garden subdivisions, 2 of 3 sections were planted. So, 2/3 of the garden space was planted. There were a lot of words there, obfuscating the simplicity of the problem. Now, if only some of the divided gardens had been planted, that would have changed things.
December 15, 2014

Algebra
Hmmm. I see h(t), but no x. I expect you meant to ask what the t-intercept means. Reiny's answer would be the one you want. Generally in problems like this, x represents the distance traveled horizontally. So, in that case, the x-intercept wold be how far away the ball hit...
December 15, 2014

7th grade math - tsk
#1 is * not ^ Looks ok to me.
December 15, 2014

maths
69 is not a fraction. d = n+4 (n+1)/(d+1) = 4/5 (n+1)/(n+4+1) = 4/5 (n+1)/(n+5) = 4/5 5(n+1) = 4(n+5) 5n+5 = 4n+20 n = 15 The fraction was 15/19
December 15, 2014

Pre-Algebra
draw a diagram. Using similar triangles, h/60 = 5/10
December 15, 2014

Calculus
f(1) = 2-3+1 = 0 df = (6x^2-3) dx So, starting from f(1), f(0.8) = f(1)+(6-3)(-0.2) = -1.8 The line is y-0 = 3(x-1) You can see the approximation at http://www.wolframalpha.com/input/?i=plot+2x^3-3x%2B1%2C3%28x-1%29 You could have started with a different value of x, say, x=0....
December 15, 2014

Calculus (math)
You want to integrate along x, so the shells have thickness dx. The volume is thus v = ∫[1,6] 2πrh dx where r = x+2 and h = y = 1/x^4 v = 2π∫[1,6] (x+2)/x^4 dx That's a nice easy integral to evaluate.
December 15, 2014

Calculus (math)
s(t) = 1/4 t^3 - 5/3 t^3 + c The displacement is s(6)-s(-1) The distance traveled is the arc length. So, what steps did you follow?
December 14, 2014

math
use the good old quadratic formula: x = (-6±√(36+96))/(-16)
December 14, 2014

Calculus (math)
dQ/dt = kQ dQ/Q = k dt lnQ = kt + c Q = c*e^(kt) since 2 = e^(ln2), that can of course be written by massaging the constants as Q(t) = c*2^(-t/k) where k=35 Q(t) = c*2^(-t/35) Since we are given no actual amounts, we can set c=1, so that as a fraction of the initial amount, Q(...
December 14, 2014

Calculus (math)
you can find useful formulas here. Pick the one for a paraboloid and use your numbers. http://www.had2know.com/academics/paraboloid-surface-area-volume-calculator.html I'm sure you can derive it by calculating the arc length and revolving the curve. The Theorem of Pappus ...
December 14, 2014

Calculus (math)
probably true. I'll show you mine if you show me yours...
December 14, 2014

Math
5 rad = 5(180/pi deg) 5pi/8 rad = 5pi/8(180/pi deg) I expect you can do the simplification.
December 14, 2014

Math
draw your triangle. The standard ones with integer sides include 8-15-17
December 14, 2014

Calculus
f(-1) = -2 f(4) = -2 f(x) is differentiable in the interval, so the conditions are met, and the theorem applies. Extra credit: We want to show that for c somewhere in [-1,4] f'(c) = 0. f'(x) = 3-2x f'(x) = 0 when x = 3/2 3/2 is within the interval [-1,4], so the ...
December 14, 2014

Calculus
y' = 15x^4 - 75x^2 + 60 So, is y'(1) = 0?
December 14, 2014

calculus
It looks like this very problem is discussed at http://tutorial.math.lamar.edu/Classes/CalcIII/StokesTheorem.aspx f(x,y,z) is different, but the surface is a paraboloid just like yours. It goes through all the steps to evaluate the integral.
December 14, 2014

Math
If you meant 36 / (2^5/8) + 7 * (3+11) = 107 then yes. The spacing helped determine what you wanted, but parentheses work even better.
December 14, 2014

Any Math Tutor Online? Help
Geez. Draw some diagrams, ok? The distance x is (a) x =12cot3° - 12cot6° (b) x =12cot3° + 12cot6° (c) x^2 = (12cot3°)^2 + (12cot3°)^2
December 14, 2014

Math
No. It is 2^3 * 11 All you want is the prime factors, and their powers.
December 14, 2014

Math
teacher tells 6 students each of those tells 6 more, for 36 brand-new people. But the total is now the original 6 plus the 36 new ones. And so on for each generation. Yiu are correct in saying that next time, there were 6^3 = 216 new people told, but the original 6 and the ...
December 14, 2014

Math
6+36+216 Don't forget the people doing the telling!
December 14, 2014

calculus
y' = 4x+(9x^2/(3x^3+1)^(3/2)) y = 2x^2 - 2/√(3x^3+1) + C Now plug in (0,2) to find C. integrate using u = 3x^3+1, so du = 9x^2 dx
December 14, 2014

Analytic Geometry
7x+y-7=0 intersects x+y+1=0 at (4/3,-7/3). 7x+y-7=0 makes an angle of 98.13° x+y+1=0 makes an angle of 135° with the x-axis. So, the bisector makes an angle of 116.56°, with slope -2 So, the equation of the line is y + 7/3 = -2(x - 4/3) 3y+7 = -2(3x-4) 6x+3y+15=0 ...
December 14, 2014

Physics
solve for t in 50+19.6t-4.9t^2 = 0
December 14, 2014

physic 210
the distance traveled is 17t + 1/2 at^2 with t=5 and a=2. So, divide that by the circumference of the wheel = 2pi*48
December 14, 2014

easy geometry
For the trapezoid, all we really need is the altitude. You can surely then find the area and perimeter. The long base is 10 cm longer than the shorter one. So, draw altitudes at the end of the short base and you will see two right triangles with base 5 and hypotenuse 10. So, ...
December 14, 2014

Math
AD = AE-DE BE = AE-AB AB=DE, so AD = AE-AB = BE You can reword that using all the "congruents" instead of = signs.
December 14, 2014

Physics
initially, all the energy is KE = 1/2 mv^2 At the peak, all the KE has become PE = mgh So, with 2v at first, there's 4 times the KE. That means 4 times the height at the peak.
December 13, 2014

Calculus 1
As usual, draw a diagram. If the angle subtended by the arc walked around the lake is θ, then the distance traveled on foot = 4θ by boat = √(32(1+cosθ)) = 8cos(θ/2) Use the law of cosines to get this. So, the total time t is t = 4θ/10 + 8/5 cos...
December 13, 2014

algebra 2
x^2+2x-35 x = (-2±√(4+140))/2 = (-2±12)/2 = 5,-7 Not sure how you got your answers, since you declined to show your work... x^2+10x+24 (x+4)(x+6) or, using the QF, (-10±√4)/2 x^2-11x+24 (x-8)(x-3) or, via QF, (11±√25)/2
December 13, 2014

Algebra
If a4a5 means a4*a5, then clearly a4=1 and a5=13, making d=12. So, a3a6 = (-11)(25) = -275
December 13, 2014

algebra 2
if you are aiming for a perfect square, then you are correct.
December 13, 2014

Math
Sorry, make that the long multiplication button.
December 13, 2014

Math
(2x-1)(3x-7) = 6x^2-17x+7 go to calc101.com and click on the long division button. Enter 6x^2-17x+7 and 4x+3 as your polynomials, and watch the fun! I'm sure you will find where you went wrong.
December 13, 2014

precalculus
(A) The denominator never zero, so the domain is all real numbers. So, of course F(x) is continuous, since there are no places where it is undefined. As x gets large, F(x) ≈ 3x^2/x^2 = 3. For the zeros of rational functions, they occur where the numerator is zero (as ...
December 13, 2014

Math
If the ladder of length z touches the ground x feet from the fence, and touches the building at height y, then z^2 = (x+2)^2 + y^2 Using similar triangles we see that x/12 = (x+2)/y y = 12(x+2)/x z^2 = (x+2)^2 + (12(x+2)/x)^2 So, find dz/dx and set it zero, to see that the ...
December 13, 2014

physics
the answer, of course, is 10.0-6.14 = 3.86 kg have been removed.
December 13, 2014

physics
since PV=nRT and RT and V are to remain constant, P/n = RT/V must be constant. n is usually in moles, but we can just as easily call it grams, since the ratio of moles to grams is constant for O2. We have reduced P by a factor of 26.4/43.0, so we must reduce the quantity of O2...
December 13, 2014

physics
1.8 (1 - 5.80/21.6) = 1.32 moles
December 13, 2014

precalculus
holes occur where the numerator and denominator are both zero. #16 x^2+2x+1 = (x+1)(x+1) 2x^2-x-3 = (x+1)(2x-3) So, f(x) = (x+1)/(2x-3) everywhere except at x = -1. At that point, f(x) = 0/0 which is not defined. The only vertical asymptote is at x = 3/2, and at x = -1 there ...
December 13, 2014

Algebra 1
2 units down sorry
December 13, 2014

Algebra 1
2 units down sorry
December 13, 2014

Algebra 1
what kind of translation? To shift the graph up k and right h, you need y-k = f(x-h) So, to shift f(x) = |x| up 2 and right 3, you have y-2 = |x-3| or, y = |x-3|+2 h and k may be negative, for shifting down and left.
December 13, 2014

Algebra 1
Write an equation for then translation of y = IXI
December 13, 2014

algebra 2
both correct
December 13, 2014

Algebra
⌊t⌋ = 2t+3 Clearly, t must be a multiple of 1/2 If an odd multiple, then we have t = (2k+1)/2 ⌊t⌋ = k 2t = 2k+1 k = 2k+1+3 k = -4 t = -7/2 If t is an even multiple of 1/2, then ⌊t⌋ = 2k/2 = k 2t = 2k k = 2k+3 k = -3 t = -3 See the graphs at ...
December 13, 2014

Algebra 1
Thank you from a 68 hear old Grandfather trying to help his Grandson
December 13, 2014

Algebra 1
What does the graph y = - absolute value of X -4 look like.?
December 13, 2014

Algebra 1
Yes I can. Thank you from a 68 year old Grandfather helping his Grandson
December 13, 2014

Algebra 1
What does the graph of y = absolute X-2 look like?
December 13, 2014

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