Wednesday
February 22, 2017

Posts by steve

Total # Posts: 48,712

Science
50m/2.8s = 50/2.8 m/s = ...
January 11, 2017

Calculus Please Help
Assuming the x values for the table are 1,2,3,4 then d/dx g(f(2x)) = g'(f(2x)) * f'(2x) * 2 = g'(f(2)) * f'(2) * 2 = g'(1) * 2 * 2 = 5*2*2 = 20 consider something like y = e^sin(2x) y'(x) = e^sin(2x) * cos(2x) * 2
January 11, 2017

Calculus
looks good to me
January 11, 2017

Calculus
Hmmm. h is constant at 12, so V = ?r^2h = 12?r^2 dV = 24?r dr ...
January 11, 2017

Math parallel lines and angles
no diagrams visible here. Just recall what you know about alternate angles and adjacent angles of transversals.
January 11, 2017

Angle Math Help!
well, you could always consider the 5-12-13 right triangle.
January 11, 2017

Geometry
I don't see how YO can divide the square. It just goes from a side to the center.
January 11, 2017

Math Calc
Hmmm 3.14*4.2^2 * 12.2 = 665.75 other than that, your logic is sound. Also, note that the error using 4.0-0.2 in for the low-side value differs by a smaller amount.
January 11, 2017

Math Calc
if 3.8 <= r <= 4.2, ?*3.8^2*12 <= v <= ?*4.2^2*12 544.32 <= v <= 665.01 ...
January 11, 2017

math algebra
15.99 + 0.93m = 259.65
January 11, 2017

math
ok
January 11, 2017

Calculus
see the further discussion on your earlier post.
January 11, 2017

Calculus
That is because x=0 is the single point where f'(x) = 0 the number zero is a single choice, not an absence of choices! The answer is 1 There is 1 (one) point on the interval [-1,1] where f(1)-f(-1) ------------ = 0 1 - (-1) That point is at x=0. Just take a deep breath and...
January 11, 2017

Calculus
Excuse me? Did you look at the graph? Did you actually read what I wrote? I don't mind helping you arrive at a solution, but I do expect you to actually read it, rather than just hold out your hand and say "gimme the answer." In fact, I did give you the answer.
January 11, 2017

Calculus
absolute value problems can get tricky, because the functions are not differentiable at any cusps. However, since (x^2-9)(x^2+1) is negative on [-1,1], f(x) = -(x^2-9)(x^2+1) This is a nice smooth polynomial, so it satisfies the requirements of the MVT on [-1,1]. Now take a ...
January 11, 2017

Calculus
v(t) = 0 at 0,?,2? If you exclude the endpoints of the interval, your answer is correct. But, we are working with the closed interval, including the endpoints. So, there are 3 points where v(t) = 0. Better review interval notation.
January 11, 2017

Calculus
v(x) = -sin(x) e^cos(x) since e^cos(x) is never zero, how many times in sin(x) = 0 in the interval? Your answer is correct on the interval (0,2?), but not on [0,2?]
January 11, 2017

Vectors
This is discussed here: http://math.stackexchange.com/questions/1408917/finding-vector-form-of-an-angle-bisector-in-a-triangle
January 11, 2017

Maths
Using x and y for syntactical reasons, See http://www.wolframalpha.com/input/?i=%7B%7B7,9%7D,%7B5,7%7D%7D*%7B%7Bx%7D,%7By%7D%7D+%3D+%7B%7B3%7D,%7B1%7D%7D
January 11, 2017

Calculus
try (lim x^3) * (lim sin(1/x)) x^3 -> 0 |sin(1/x)| <= 1
January 11, 2017

Maths
1 degree of latitude is about 111 km. So, 800 km/hr ? 800/111 = 7.2°/hr so, ...
January 11, 2017

Maths
Check the diagram. The radius of the latitude at angle ? is r*cos?. Since speed is proportional to the radius of rotation, if B is at angle ?, r cos22° = 2r cos?
January 11, 2017

math;););)
so, do you know the rotation matrix?
January 11, 2017

Math;);)
Actually, it's even better than that: |u + v|^2 ? |u|^2 + |v|^2 ? (|u|+|v|)^2
January 11, 2017

Calculus
since when is x^2/x^2 = 2? 10/10 = 1 z^3/z^3 = 1 don't forget your Algebra I now that you're taking calculus. Using the usual method, divide top and bottom by x^2. That gives you (1 + 2/x^2)/(1 - 36/x^2) as x^2 gets huge, 1/x^2 -> 0 and the fraction becomes 1/1 NOT 2!!
January 11, 2017

Calculus
as x gets huge, the 2 and the 36 become insignificant: y -> x^2/x^2
January 11, 2017

Physics
40 S = <0,-40> 70 N30ºW = <-35,60.6> add them up, then convert back to compass directions.
January 11, 2017

Math
1700 * .96*9
January 10, 2017

calculus
a = t^2-5t+3 v = 1/3 t^3 - 5/2 t^2 + 3t + C1 s = 1/12 t^4 - 5/6 t^3 + 3/2 t^2 + C1*t + C2 Now use the conditions to solve for C1 and C2.
January 10, 2017

pre-Calculus
a: odd b: even c: unknown check by using the fact that odd: f(-x) = -f(x) even: f(-x) = f(x)
January 10, 2017

Math
100/(b+24)
January 10, 2017

Trig
If the base is 2x, then 12.5/x = tan 55° The area is just 12.5x
January 10, 2017

Math
-.25x^2+5.5x-5.25 = -1/4 (x^2-22x) - 21/4 = -1/4 (x^2-22x+121) - 21/4 + 121/4 = -1/4 (x-11)^2 + 25
January 10, 2017

Math
8C4
January 10, 2017

Math
w(w+5) = 50 Now, which factors of 50 differ by 5?
January 10, 2017

Algebra
4a-2b+c = 5/2 c = 3/2 16a+4b+c = -121/2 F(x) = -5/2 x^2 - 11/2 x + 3/2
January 10, 2017

Math
just plug in the numbers. What do you get?
January 10, 2017

Math
there are only a few factors of 32, all of them powers of 2. It must have 2 digits, so there is only one that fits.
January 10, 2017

Math
well, they surely end in 3, so look up a list of primes and add them up.
January 10, 2017

Trig/PreCalc
as t changes from 0 to 1, x changes by -7 y changes by -6 x = 5-7t y = 2-6t
January 10, 2017

Trig/PreCalc
t = y-2 x = 5-3t = 5-3(y-2) It is clearly a line.
January 10, 2017

Trig/PreCalc
If we label the points A,B,C, then AB=?84 BC=?41 AC=?85 85 = 84+41-2?84?41 cosB Now you can use law of sine or cosine for one other angle, and then the angles sum to 180.
January 10, 2017

Math
A = 2/3 b b = 3/4 c a+b+c = 8200 Now just solve for c.
January 10, 2017

Chemistry
For the following reactions, determine the equilibrium constant equation. 1) CO2(g) + H2(g) CO(g) + H2O(g) 2) 2NO(g) + 2H2(g) N2(g) + 2H2O(g) 3) Cu(s) + 2Ag+(g) Cu2+(g) + 2Ag(s) 4) H2(g) + I2(g) 2HI(g)
January 10, 2017

Pre Calc
{1}
January 10, 2017

Math
if the dimensions are x,y,z then there are 3 pairs of parallel faces. The area is thus 2xy + 2xz + 2yz Now just plug in your numbers.
January 10, 2017

algebra
what two factors of 32 differ by 4? y = (x-8)(x+4) the discriminant is b^2-4ac = 16+128 = 144
January 10, 2017

Algebra
use what you know about arithmetic sequences, in this case a = 1 d = 2 n = (49-1)/2 + 1 = 25 S25 = 25/2 (1+49)
January 10, 2017

algebra
you know that the axis of symmetry is at x = -b/2a = 4/2 = 2 Symmetry means that the two roots are equally spaced on either side of the axis.
January 10, 2017

algebra
42
January 10, 2017

algebra
4*3*2 = 24 5184/24 = 216 = 6^3 ... Or, more usually you will be asked to solve 4x * 3x * 2x * 5184
January 10, 2017

algebra
2b+2 = 4b-46
January 10, 2017

Graphing in the Coordinate Plane Unit Test
if you cannot plug in the values and evaluate the expression, you are in deep trouble. For example, is (5,3) a solution? -4(5)-9 = -29 Nope, not equal to 3.
January 10, 2017

trig
duplicate posts are a waste of time, both yours and ours...
January 10, 2017

math
draw a diagram review your basic trig functions. (h-5)/90 = tan 81°
January 10, 2017

Math
all correct.
January 10, 2017

geometry
Totally!
January 10, 2017

Math grade 6, quadrilateral logic
Hmmm. I thought a trapezoid was a quadrilateral with only one pair of parallel sides. I guess it depends on who is doing the defining...
January 10, 2017

Math
see your previous post.
January 10, 2017

algebra 2
What is the s9mplermform of the radical expression? sqrt36g^6 my answer is 6lg^3l
January 10, 2017

Algebra2
?5 * 3?5 = ?5*?5 * 3 = ...
January 10, 2017

Algebra2
Find the product sqrt 5 times 3sqrt5
January 10, 2017

math
Looks like C to me. Draw a line and locate points P and Q. Now, note that R can be on either side of P.
January 10, 2017

geometry
see http://www.ask-math.com/constructing-triangles.html
January 10, 2017

Math science etc
google is your friend: http://www.ask-math.com/constructing-triangles.html
January 10, 2017

9th grade algebra (recursive formula)
You're welcome. As for the notation, I'm not sure it's "correct" or standard. I just thought of using it since making subscripts is a pain, and the parentheses sometimes get confused with function notation. You will also see An, An+1 (ambiguous: cf. (An)+...
January 10, 2017

9th grade algebra (recursive formula)
a<18> = a<1> + 17*200 = 3362 So, a<1> = -38 similarly, a<21> = a<1> + 20*0.6 = -1.4 now again, just solve for a<1> a<n> = a + (n-1)d
January 10, 2017

math
12c+b
January 9, 2017

Math
hint: a and w are times, and add to 12.
January 9, 2017

Math
You have a slight(!) error: R = 100/?q * q = 100?q Profit = R-2q-1200 = 100?q - 2q - 1200 maximum profit where dP/dq = 0 50/?q - 2 = 0 50 = 2?q q = 625 since P = R-C, dP/dq = 0 when dR/dq = dC/dq The price is 100*25 = 2500
January 9, 2017

Trigonometry
Just recall that C = 2pi * r
January 9, 2017

Math
the sides are equal, so 4a = 3b 4a = a+b+c c = 3a-b, so 4(3a-b) = 3b 12a-4b = 3b 12a = 7b subtracting, 8a = 4b or 4a = 2b But, 4a = 3b, so 2b = 3b b=0 You only supplied two equations for three variables, and 0 is not a likely solution. Check for typos and try again.
January 9, 2017

math
sin(theta) = y/r just to remind you, r^2 = x^2+y^2
January 9, 2017

algebra sir reiny sir steve&bob damon help
By inspection, it should be clear that 3*3^2 = 3^3 There is another solution, at about x = 0.4844 but you won't arrive at it algebraically. You can tell that 3 * 1/4 ? ?(1/2) 0.7500 ? 0.7071
January 9, 2017

MATHS
consult your trig text, or just google its images. sheesh ...
January 9, 2017

Math
since he wants 4 times the recipe, the cups turn to quarts: He will need 1.25 qt
January 9, 2017

Geometry
since BD bisects ABC, mABD = mDBC, and they add up to mABC: 9x = 2(4x+38)
January 9, 2017

MATH
rats: ?3y y^6 z -------------- x
January 9, 2017

MATH
?3 = 3^.5 z^0 = 1 So, we can write this as x^4 y^.5 z 3^.5 ------------------- = (y^6.5 3^.5/x) = ?(3y)y^6/x y^-6 x^5
January 9, 2017

math
3.5mi/22.25min = 0.157 mi/min
January 9, 2017

Math
84.06 m 8406 cm
January 9, 2017

math
48*8 + 54*9 = ?
January 9, 2017

Math
320rs / (5rs/m^2) = 64 m^2
January 9, 2017

math
well, he made 5.18-2.32 = $2.86 on each shirt, so ...
January 9, 2017

Math
the side length of the field is 32000/16 / 4 = 500 meters So, now you can get the area, and thus the cost.
January 9, 2017

Algebra
and did you check your answer? 2*4+2 = 10 4-3*2 = -2 yes, it works.
January 9, 2017

Math
huh? what are x and y?
January 9, 2017

AP Calculus
It depends on how far away B is when sighted. If it is k km north and west, then the distance z between the ships after t hours is z^2 = (k-3t)^2 + (k-8t)^2 = 73t^2-22kt+k^2 dz/dt = (73t - 11k)/?(73t^2-22kt+k^2) dz/dt=0 when t = 11k/73 so, the minimum distance is z = 5k/?73
January 9, 2017

Pre-Calculus
x(160-2x)
January 8, 2017

Math
as always, for y=ax^2+bx+c, the vertex is at x = -b/2a = -3 f(-3) = -(b^2-4ac)/(4a) = -4
January 8, 2017

calculus
You have to be kidding!! The entire area is only growing at 3 in^2/s. You need to learn to do a sanity check on any answer you get, especially in a new situation. Using the given equation and numbers, we have 3 = 2?*10 dr/dt dr/dt = 3/(20?) = 0.0477 in/s Your answer is 60?. ...
January 8, 2017

calculus
well, a = ?r^2 da/dt = 2?r dr/dt ...
January 8, 2017

MATH
well, the height y at time t is y = 33 + 64t - 16t^2 So, solve for t when y=48. The max height is of course, when t = 64/32 = 2. I expect you can determine the range... (restrict it to the domain involved.)
January 8, 2017

Math
There are 2^3-1 = 7 ways to choose at least one stamp.
January 8, 2017

Calculus
y = 1-x z = xy = x(1-x) now just use what you know about parabolas. No calculus needed here. Of course, you can verify that the max occurs at the vertex...
January 8, 2017

calculus
I'll do (b) to show the way. Of course, you probably already know the way... Assuming you meant f(x) = x^3+x-4, f(-2) = -14 f(3) = 26 slope of secant is 40/5 = 8 f' = 3x^2+1 3x^2+1 = 8 3x^2 = 7 ... clearly, ?(7/3) is in [-2,3]
January 8, 2017

Math
4" is 1/3 foot. So, (h - 1/3)^2 + 4^2 = h^2 Damon is correct. 24'2"
January 8, 2017

math
Let the plane be x west, and the jet be y south of St. Louis. Draw a diagram. Then the distance z between the two aircraft is z^2 = x^2+y^2 At the moment in question, 300^2 = 100^2+y^2 y = 100?8 z dz/dt = x dx/dt + y dy/dt 300 dz/dt = 100(-500) + 100?8 (-600) dz/dt ? -732 mi/hr
January 8, 2017

calculus
f(1) = -3 f(2) = 12f(1) = -36 ... Clearly, f(n+1) = -3*12^n
January 8, 2017

math
Draw a diagram. If the man is x feet from the tower, and his shadow is s ft long, then using similar triangles, s/6 = (x+s)/40 s = 3/17 x ds/dt = 3/17 dx/dt ...
January 8, 2017

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