Sunday

January 22, 2017
Total # Posts: 47,949

**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*

**Math**

x^2y = 800 y = 800/x^2 c = 6*x^2 + 2*x^2 + 5*4*xy = 8x^2 + 1600/x dc/dx = 16x - 1600/x^2 = 16(x^3-100)/x^2 dc/dx=0 at x=?100 so, the shed is ?100 x ?100 x 8?100

*January 8, 2017*

**Maths**

(6-0)/(3-(-4)) = 6/7

*January 8, 2017*

**math**

22 > 6.3, right?

*January 8, 2017*

**Trig**

the period is 2?/n so, the solutions are ?/6n + k(2?/n) = ?/6n (12k+1) 5?/6n + k(2?/n) = ?/6n (12k+5) for all integers k.

*January 8, 2017*

**math linear equation**

If the larger is x, then x/5 = 8 + (110-x)/9

*January 8, 2017*

**Math(simple interest)**

.05(n-1)x = 736 .0375nx = 736 Now just solve for x, then double it.

*January 8, 2017*

**Math**

In a cyclic quadrilateral, opposite pairs of interior angles are always supplementary - that is, they always add to 180°. Now, what do you know about opposite angles of a parallelogram?

*January 8, 2017*

**Geometry**

well, heck - just draw one. What do you see?

*January 8, 2017*

**Math**

(10a+b)= 2(a+b)+2 b = 8a-2 So, what choices are there? a=1 b=6 a>1 : 8a-2 is too big for a single digit b. So, 16/7 = 2 r 2

*January 8, 2017*

**Math**

12+x + 345+x + 126+x = 975 Now just solve for x.

*January 8, 2017*

**Math**

Let the jugs hold x and y liters. x-1 = y y-2 = x/2 The jugs hold 6 and 5 liters.

*January 8, 2017*

**Math**

4" = 1/3 ft so, reviewing your diagram, (h - 1/3)^2 + 4^2 = h^2 h = 145/6 = 24'2"

*January 8, 2017*

**Maths**

well, the diagonals are equal, so 2x = 3x+1 I suspect a typo.

*January 8, 2017*

**Algebra2**

What is the simplest form of the quotient? ^4?810/^4?2

*January 7, 2017*

**algebra**

360 <= 87+96+91+x 86 <= x

*January 7, 2017*

**maths**

since the brick dimensions divide the road dimensions evenly, it does not matter which way the bricks are laid (assuming that the brick's edges are parallel with the road's). So, we can just divide the area of the road by the area of a brick: (100m * 20m)/(.25m * .10m...

*January 7, 2017*

**science**

so, how many moles of AgNO3 are needed? multiply that by 170 g/mol

*January 7, 2017*

**math**

.53x = .47x + 9600

*January 7, 2017*

**Algebra2**

there are none - it is negative. However, the real roots of 9/16 are +3/4 and -3/4

*January 7, 2017*

**Algebra2**

Find all of the real square roots of -9/16.

*January 7, 2017*

**Maths**

When the water has depth y, the surface has radius y/4 v = 1/3 Vy^2h = ?/48 y^3 dv/dt = ?/16 y^2 dy/dt Now use you numbers to find dy/dt

*January 7, 2017*

**History**

How did World War II change the population of Arizona?

*January 7, 2017*

**algebra**

3j(j^2-17j+70) = 3j(j-10)(j-7)

*January 7, 2017*

**algebra**

3(15g^2+4g-3) = 3(3g-1)(5g+3)

*January 7, 2017*

**algebra**

which factors of 54 add to 15? Just consider the pairs: 1 54 2 27 3 18 6 9

*January 7, 2017*

**Math**

so, where are E and F?

*January 6, 2017*

**algebra word problem**

the nice wikipedia article on trajectory gives the equation, including the angle involved.

*January 6, 2017*

**Algebra**

how can y be negative? x+y+z = 54000 .08x + .06y + .09z = 4260 .08x = 6*.06y x,y,z = 36000, 8000, 10000 ----------------------------------- So, where did you go wrong? 8x+6(9y)=0 Why do you think the interest sums to zero?

*January 6, 2017*

**algebra**

G <= 2

*January 6, 2017*

**Math**

come on, man! It's still ?2u^(2/3) du = 2 (3/5) u^(5/3) + C = 6/5 (x^2+2x-3)^(5/3) + C

*January 6, 2017*

**Math**

I suspect a typo. You probably meant ?(4x-4)(x^2-2x-3)^(2/3) dx or ?(4x+4)(x^2+2x-3)^(2/3) dx Assuming the first, Let u = x^2-2x-3 du = 2x-2 dx Then you have ? 2u^(2/3) du which is easy. ... right? If there is no typo, you are in deep trouble.

*January 6, 2017*

**Math**

1+i = ?2 cis ?/4 (1+i)^101 = (?2)^101 cis (?/4 * 101) = 2^50 ?2 cis (25? + ?/4) = 2^50 ?2 cis 5?/4 = 2^50 (-1-i) or -2^50 (1+i) There appears to be a typo.

*January 6, 2017*

**math**

what do you mean 4y=6y-2x+1 ?? Why not just say 2y = 2x-1 If that is the case, then we have 2(2x-1) + x+2x-1 = 28 Use that to find x, and then y. If there's a typo in the problem, fix it and use the same logic.

*January 6, 2017*

**Math**

8000 * 0.095 * 120/365

*January 6, 2017*

**math - eh?**

by "cover the entire room" do you mean all the walls, floor, and ceiling? Strange use for border.

*January 6, 2017*

**maths**

Not sure what you mean. The angle of reflection on the surface is always equal to the angle of incidence. The critical angle for total internal reflection decreases with increasing index of refraction.

*January 6, 2017*

**More calculus**

the fence length f = 2r + r? since the area is constant, 1/2 r^2 ? = A ? = 2A/r^2 so, f(r) = 2r + 2A/r Now just find r where df/dr = 0 Use that to get ?

*January 6, 2017*

**Calculus**

You have the right idea. But a must be chosen so that lim (ax-10) = 1 as x->3+ f(x) is defined every where except at x=3, so define it to be 1 there, since the limit from both sides is 1. That is, f(3) = B a = 11/3 B = 1

*January 6, 2017*

**Math**

true for any number except zero.

*January 6, 2017*

**calculus**

the points are (4,1) and (4,-1). -2x + 4yy'+3 = 0 y' = (2x-3)/(4y) So, now you have a point and a slope, and the lines are y-1 = (x-4) y+1 = -(x-4) See http://www.wolframalpha.com/input/?i=plot+-x%5E2%2B2y%5E2%2B3x%3D-2,+y-1%3Dx-4,+y%2B1%3D-(x-4)

*January 5, 2017*

**Algebra2**

rearrange things to 3x^2+6x-5 = 0 Now use the quadratic formula.

*January 5, 2017*

**Algebra2**

Which expression gives the solution -5+2x^2=-6x?

*January 5, 2017*

**calculus**

5y + 5xy' + 2xy + x^2 y' = 0 Now collect terms and solve for y'

*January 5, 2017*

**Calculus**

f' = 3h^2 h'

*January 5, 2017*

**Math**

.450km / 10km/hr = .045 hr

*January 5, 2017*

**pre calc**

do this just like your previous exercise.

*January 5, 2017*

**math**

They are separating at a rate equal to the slower truck's speed. Since It took 6 hours to separate by 204 miles, that is 204mi/6hr = 34 mi/hr So, the slower truck is going 34 mi/hr You found the faster truck's speed, but then botched it again since 2*8 ? 146 !!

*January 5, 2017*

**pre calc**

If x is at 6%, then the rest y=(3000-x) is at 7%. So, x+y = 3000 .06x + .07y = 194.00

*January 5, 2017*

**Calculus**

look up the arc length. The particle must move along a curve. At each small interval, the curve can be considered a straight line, with "arc length" ds^2 = dx^2 + dy^2 Thus, adding up all the tiny hypotenuses gives. s = ?ds = ??(dx^2+dy^2) = ??(1+(y')^2) dx

*January 5, 2017*

**Math Calc**

I assume you mean y = 3x^(1/3) + 6x^(4/3) = 3(2x+1) x^(1/3) y' = x^(-2/3) + 8x^(1/3) = (8x+1) x^(-2/3) y" = -2/3 x^(-5/3) + 8/3 x^(-2/3) = 2/3 (4x-1) x^(-5/3) y'=0 at x = -1/8 y"(-1/8) < 0 so y(-1/8) is a maximum y"=0 at x = 1/4 so that is an ...

*January 5, 2017*

**math**

double the 1st equation and you have 6x-2y = -6 It is clear to see that since -6 ? -8 the two equations cannot have a single solution. The lines are parallel, and do not intersect.

*January 5, 2017*

**Pre calc**

adjust things a bit to get 6x+12y = 57 -12x+12y = 12 subtract and you get 18x = 45 x = 5/2 Now use that to find y. Or, note from the 2nd equation divided by 3 that -x+y=3 y=x+1 Use that in the 1st equation to get 2x+4(x+1) = 19 2x+4x+4 = 19 6x = 15 x = 5/2

*January 5, 2017*

**pre calc**

add the two equations to get 0 = x-1 x = 1 now use that to get y.

*January 5, 2017*

**Algebra**

f+s = 106 f+3 = 2(s-4) now crank it out.

*January 5, 2017*

**math**

PV=kT So, PV/T = k a constant. So, you want T such that 48*1/T = 1*16/305

*January 5, 2017*

**Math**

Any line not in the plane of GH is skew to GH. Skew lines necessarily cannot intersect. Not having any details of your diagram, it's hard to say much more. Maybe google can provide you with further relevant examples.

*January 5, 2017*

**math**

Try this. I just googled ABCD is aparallelogram in which BCis produced to E such thatCE = BC and got this hit, among others: http://www.meritnation.com/ask-answer/question/abcd-is-a-parallelogram-in-which-bc-is-produced-to-e-such-th/areas-of-parallelograms-and-triangles/...

*January 5, 2017*

**math**

F=ma v = at = Ft/m so, t = vm/F = 2.8*10^3*7.9 /6.7*10^5 = 0.033 seconds

*January 5, 2017*

**math**

a = v^2/(2s) = 0.614/0.744 = 0.8263 m/s^2 F = ma = 61.0*0.8263 = 50.34N

*January 5, 2017*

**math check my answer ?**

as written, f(x) has a range of all real numbers. Pick any value for f(x), and you can easily find an x to produce it. For example, suppose you want f(x) = 11 -3x-1 = 11 -3x = 12 x = -4 So, you must have a typo. Your range of f < -1 could be produced with f(x) = -3x^2 - 1 f...

*January 5, 2017*

**geometry**

a = 1/2 r^2 ? Use that once you supply the missing data.

*January 5, 2017*

**Science**

google is your friend. Try it.

*January 5, 2017*

**math**

g = 12.50 r = 0.75g y = 2.5r = 2.5 * 0.75 * 12.50 = 23.4375 or, using mixed numbers, y = 2 1/2 * 3/4 * 12 1/2 = 23 7/16

*January 5, 2017*