Saturday
August 1, 2015

Posts by steve


Total # Posts: 32,558

Trigonometry
Looks good to me. I'd go with the +3cos(2θ + 3π/2)-3 since the cosine function is what is being given, not a flipped or shifted cosine.
June 4, 2015

math
looks like you're all set to use the distance formula. So plug in your numbers, as you have declined to share them with us.
June 4, 2015

Computers
I score it 2+4+0+3+2=11/20
June 4, 2015

Applications: Percents
After n years, the interest is prn. So, you want (20500)(.06)n = 5535 n = 4.5 years To double, you need .06n=2, or n=33.3 years
June 4, 2015

Find the GCF of the monomials
3x is the largest factor that divides all three monomials. So, it is the GCF. Trent: Since the terms have not been added, there is no sense in trying to factor it. In any event, assuming such a sum would have yielded 3x(y+2z+3yz)
June 4, 2015

Chem.
pressure has increased by a factor of 1.165/0.973 = 1.197 1.197 * 0.250 = 0.299 So, 0.049 mols were added. (Probably 0.05)
June 4, 2015

Chemistry
22.4 Mol/L at STP means 44.8 moles of H2 Each mole of Zn produces one mole of H2, so you need 44.8 moles of Zn. How many grams is that?
June 4, 2015

math help
quadratic sequences will have linear 1st differences and constant 2nd differences. The 1st differences here are 5,x-9,37-x The 2nd differences are x-14,46-2x If x=20, that makes the 1sts: 5,11,17 and the 2nds 6,6 which is consistent. I expect you can determine the nth term all...
June 4, 2015

math
ax^2+bx=bx^2+a (a-b)x^2 + bx - a = 0 The discriminant is b^2 + 4a(a-b) = b^2-4ab+4a^2 = (b-2a)^2 since that is a perfect square, plugging it into the quadratic formula will always yield a rational result if a and b are rational. Note that the question is invalid if a or b is ...
June 4, 2015

Math
So, lay out the jeans in a row. There are 5 pairs. Pick the first one. There are 5 ways to do it, right? That leaves 4 pairs to choose the other one you want. There are 4 ways to pick that one. So, for each of your first 5 choices, you have 4 other choices, making 5*4 = 20 ...
June 4, 2015

math help
Assuming you mean 3^x = 81 - 3^x 2*3^x = 3^4 log32 + x = 4 x = 4 - log32 Somehow I suspect a typo.
June 4, 2015

math
since sec^2 = 1+tan^2, you have 2+2tan^2 + tan^2-3 = 0 3tan^2 = 3 tan^2 = 1 tan = ±1 now, where is that true?
June 4, 2015

math
x^2+4y^2+6x-8y+9=0 x^2+6x + 4y^2-8y = -9 x^2+6x+9 + 4y^2-8y+4 = -9+9+4 (x+3)^2 + 4(y-1)^2 = 4 (x+3)^2/4 + (y-1)^1 = 1 Now the rest should be easy. Come on back if you get stuck.
June 4, 2015

Math
as always (a) draw a diagram (b) review your basic trig functions Then it will be clear that tanθ = 300/50
June 4, 2015

math
2x^2-2x-24 2(x^2-x-12) 2(x-4)(x+3)
June 4, 2015

math
suppose you had f(x) = 4-x^2 The roots would be x = ±2 4-(x+1)^2 is the same graph, just shifted left by 1, so its roots are x = -1±2 = -3,1 See http://www.wolframalpha.com/input/?i=-%28x%2B1%29^2%2B4
June 4, 2015

Math: Arithmetic Sequence.
a3 and a16 are 13 terms apart. So, 13d = 47-8 = 39 d=3 a+2d=8, so a=2 Now you know a and d.
June 4, 2015

maths
Hmm. I was looking for a cute way, but I guess I'll just have to brute-force it. secx + tanx = m secx(1+sinx) = m 1+sinx = m cosx (1+sinx)^2 = m^2 cos^2 x sin^2 + 2sin + 1 = m^2 - m^2 sin^2 (1+m^2)sin^2 + 2sin + 1 = 0 now solve that using the quadratic formula. Because of ...
June 4, 2015

geometry
you know by now that the standard equation for a circle with center at (h,k) and radius r is (x-h)^2 + (y-k)^2 = r^2 So, just plug in the numbers above. And see your other posting for a similar answer.
June 4, 2015

maths
first step: arrange terms in descending power 8s^2+14s-14 = 0 now you can divide by 2 just to use smaller numbners: 4s^2+7s-7 = 0 Now use the quadratic formula: s = (-7±√161)/8
June 4, 2015

math
a = 12/b^4, so (12/b^4)^5 b^5 = 7776 12^5/b^15 = 7776 b^15 = 32 b = ∛2 so, a=12/∛16 = 6/∛2
June 4, 2015

C programming
usually arrays are declared with type name[]; or type name[n]; or type* name;
June 3, 2015

Science
acceleration from gravity of any object on earth is -9.81 m/s^2 Is there more to this question?
June 3, 2015

physics
s = v^2/2a solve that for a, and the F=ma.
June 3, 2015

math
If the apparent heading of the plane is (65+θ)°, and the plane's speed is v, then 60+v*sin65° = 750 sin(65+θ)° 750 cos(65+θ)° = v cos65° v = 695 and θ=1.6° So, the plane needs to fly at N66.6°W and the plane's ground ...
June 3, 2015

Math 7
draw a diagram. Using similar triangles, you can see that if the tree has height h, h/25 = 10/6 The ratio of height:shadow is the same for both pole and tree.
June 3, 2015

Consumer math
^ and log are inverse operations x+8 - 8 = x x/8 * 8 = x (√x)^2 = x log88x = x 8log8x = x The thing that makes logs initially so confusing is the notation. If we had a cute symbol like + or / or √ things would be a lot easier. The definition of log8x is that power ...
June 3, 2015

Astronomy
If you are talking about the time when the planets are on the same side of the sun, then only the planets outside Mars' orbit would exhibit retrograde motion, since Mars travels faster in its orbit.
June 3, 2015

Algebra
If the width, length, height are x,y,z then you know that 2(xy+xz+yz) = 160 y = 2x y = z-4 Now just make some substitutions, and you will find that z=9
June 3, 2015

math
if there are x 6d nails, and y 10d nails, then you have been told that x+y = 8 x = y+2
June 3, 2015

Algebra
apparent to whom? measured in what units? The shuttle does not orbit on the surface of the earth, so at what altitude?
June 3, 2015

math help
Don't know what's missing, but since you have a - sign, I'll sssume your + key is malfunctioning. If we go with x-3+2y=0 then x = 3-2y Plug that into the other equation and you have 2y^2-3(3-2y)^2-4(3-2y)y=9 or, 2y^2-24y+36 = 0 Then, using the quadratic formula, y...
June 3, 2015

Math
maximize p=3x+6y subject to 6x+9y <= 300 5x+4y <= 180 Now just draw the lines and find the vertices. There are many helpful online sites to verify your work. One is at http://www.zweigmedia.com/RealWorld/LPGrapher/lpg.html
June 3, 2015

Geometry
The solution to the last one didn't take? Take another look at it, and try your hand on this one.
June 3, 2015

physics
since velocity involves final displacement, not total distance covered, you have 3km/25.5min = 0.1176 km/min in the direction from start to finish.
June 3, 2015

Geometry
180(n-2) = 10800
June 3, 2015

Math
15: 9*7 x 10^(6+5) do #16 in like wise.
June 3, 2015

physics
f1 = <-31.82,31.82> f2 = <44.55,44.55> r = <-8.49,8.49> f3 = <x,y> where -31.82+44.55+x = -8.49 31.82+44.44+y = 8.49 Now just find x and y.
June 3, 2015

math
The differences are 4,6,8,10,12,... The 2nd differences are 2,2,2,... That means it's a quadratic. a+b+c = 1 4a+2b+c = 5 9a+3b+c = 11 Looks like An = n^2+n-1 So, when is n^2-n-1 = 2549 n^2-n-2550 = 0 (n+50)(n-51) = 0 Looks like A51 = 2549
June 3, 2015

Geometry
Alas? All was good up till there. The standard equation desired is indeed x^2 + (y-2)^2 =4
June 3, 2015

Geometry
(x-0)^2 + (y-2)^2 = 2^2
June 3, 2015

math
Sorry. 3x^2 kx-k makes no sense. Is it 3x^2+kx-k or 3x^2-kx-k ? As it stands, since a b means a*b, you have 3x^2*kx-k = 3k 3kx^3-k = 3x 3kx^3-3x-k = 0 which clearly does not work.
June 3, 2015

math
You are missing a + or - sign in there.
June 3, 2015

Algebra 1
221-150 = 71, which is 43 std above the mean!!! Look that up in your Z table! I suspect a typo.
June 3, 2015

Math
You have 2^3 x^-9 y^12 ----------------------- 4^2 x^2 y^2 which is y^10 / 2x^11
June 3, 2015

Geometry.
Hmm. Looks to me like ∠D corresponds to ∠A = 24°
June 3, 2015

sat math
99+99 = 198 B+C = 17 The only way you could get more than that would be if the number ended in 99. But NR+RN = 11(R+N) so R+N would have to end in 99. I think you can see why that cannot be so.
June 3, 2015

Math
since distance = speed * time, he went 8(1/2) + 55(24/60) miles
June 3, 2015

math
42
June 3, 2015

Math
The height changed by -0.5m in one hour. That means that it was 1.71m slightly before it fell to 1.7m. Its rate of change between 9 and 10 am was -0.5 m/hr. So, it was .01 hours before 10 am when the height was 1.71m. .01 hrs = 0.6 minutes, or 36 seconds. So, the height was 1....
June 3, 2015

Derivatives Instantaneous rate of change
another way to write that is E = Kr^-2 so, using the power rule, dE/dr = K(-2r^-3) = -2K/r^3
June 3, 2015

Math
As you figured, 19 January starts 66 hours from x=0. So, you want values of x between 66 and 90 (midnight on Jan 19) You can see that there are two periods during that time when y >= 1.7 http://www.wolframalpha.com/input/?i=plot+y+%3D1.05+sin%282pi%2F11.72+x%29+%2B+1.55%2C+...
June 2, 2015

Math
however, if you are solving an equation, such as -x^2 - 5x + 4 = 0 you can multiply both sides by -1 to get rid of the leading minus sign: x^2 + 5x - 4 = 0 since -0 = 0.
June 2, 2015

Maths
assuming a 360-day year, that would be 598 * 0.0775/360 * 186
June 2, 2015

Math
You have y= 3(-4x-2)^2 + 5 = 3(16x^2+16x+4)+5 = 48x^2+48x+17 Now, f = x^2, so x = √f That makes y = 48f + 48√f + 17
June 2, 2015

Math
looks good to me.
June 2, 2015

Math
you have f for 0,1,2,3,4 Clearly, since g(x) = -f(2x+3) g(-3/2) = -f(0) = 0 so (-3/2,0) g(-1) = -f(1) = -4 so (-1,-4) and so on
June 2, 2015

math
Nope. When dividing, subtract powers. What you have is x^14/x^2 That is the same as x x x x x x x x x x x x x x --------------------------------- x x Two of the x's cancel, leaving 12 in the numerator: x^12
June 2, 2015

Pre-Algebra
2x^2+8-4x+3x-6x^2+7 Collect the coefficients of like powers: (2-6)x^2 + (-4+3)x + (8+7) -4x^2 - x + 15
June 2, 2015

Math help please
input|1| 2| 3| 4|5 output|9|15|21|27|33 Note that y increases by 6 for each increase of 1 in x. So, your rule will look like y = 6x But, using x=1, 6x=6, but y=9. So, we're too low by 3. That means y = 3+6x You can easily verify that this rule works for the other entries ...
June 2, 2015

Math
q = d+8 n = 5q 5n+10d+25q = 700 Now just plug and play!
June 2, 2015

calculus
Well geez. Try amazon.com They will list dozens of calculus books, most of which will be for first-year calculus classes. Or just visit your nearest used-book store. They will surely have several.
June 2, 2015

algebra A055,
so, how many times you gonna post the same flaming problem?
June 2, 2015

algebra A055,
you just need t where -0.075t + 3.85 < 3.5 0.075t > 0.35 t > 4.67 So, any year after 1935
June 2, 2015

Math
8 * 180/pi = 458.4 Even without knowing that, you know that 8 > 2pi, so 360 is the closest of the choices.
June 2, 2015

Math
you are correct, since (-4,6) is in QII. Recall that cosine is x/r. r^2 = 4^2+6^2 = 42 r = √42 = 2√13 so, your cos is -4/2√13 = -2/√13 Or, as they clumsily put it, -2√13/13
June 2, 2015

algebra Please help
the max height is at the vertex of the parabola. You know that for at^2+bt+c, the vertex is at t = -b/2a. Then use that to find h of the vertex.
June 2, 2015

algebra
you just need t where -0.075t + 3.85 < 3.5 0.075t > 0.35 t > 4.67 So, any year after 1935
June 2, 2015

AlgebraII
You do have some signs mixed up, all right... (2x+3)(3x-2) = 6x^2+5x-6 so, -(2x+3)(3x-2) = -(6x^2+5x-6) = -6x^2-5x+6
June 1, 2015

Calculus
convert headings (not bearings!) to x-y coordinates and add them up: 724@30° = (362,627) 32@90° = (32,0) addthem up and you have (394,627) √(394^2+627^2) = 740.5 90-arctan(627/394) = 32.2° Note that the proposed solution of 57.9° is measured from the x-...
June 1, 2015

math
#1 Nope (9-5)m+(6-6) = 4m+0 = 4m #2 ok #3 Nope (6-9)h+(1+4) = -3h+5 #4 Nope (-7-(-5))w^2 + (-2-3)w + (-1-(-2)) = -2w^2-5w+1 You have a problem with subtraction?
June 1, 2015

Math
4" = 1 /3 ft 4" x 4" = (1/3 ft)(1/3 ft) = 1/9 ft^2
June 1, 2015

MATH URGENT
that would be (f(-1)-f(-4))/(-1 - -4) = (-9-0)/3 = -3 See the graphs at http://www.wolframalpha.com/input/?i=plot+y%3Dx%5E2%2B2x-8%2Cy%3D-3x+-+12+for+-5+%3C%3D+x+%3C%3D+0
June 1, 2015

Math: 5th Grade
after the sale, she had r-624 red and r yellows, so r = 4(r-624) 3r = 2496 r = 832 check: 832-624 = 208 832 = 4*208
June 1, 2015

Math
I think the question is poorly posed. Surely there is no largest number which is not divisible by 7,11 or 30. Just take any huge product of powers of those numbers and add 1, such as 7^3 11^5 30^4 + 1
June 1, 2015

math
how many mcg/min? And is that micro or milli grams? mg = milli ug = micro
June 1, 2015

physics
Many times greater. You have the two equations. Plug in the numbers. The ratio of electric to gravitational force is Kq^2/Gm^2 = 4.1x10^48 That's quite a difference!
June 1, 2015

Math
can't draw a state machine here, but you should include states such as 0: outputs an F and loops back unless an a is received, when it transitions to state 1: outputs an F and goes back to 0 unless a b is received, when it outputs a T. You haven't said what it does ...
June 1, 2015

DISCRETE MATH
clearly B is the set of positive multiples of 52.
June 1, 2015

algebra
if $x in A, then x+3000 was in B. .08x + .05(x+3000) = 1320
June 1, 2015

Math - Thanks, Reiny
Good job. I should have seen that the vertices would be where to divide the lines. My bad!
June 1, 2015

Math
not sure what you mean by "gets to advanced." Not sure why you used slashes ? instead of the real symbol |. so, we have s(x) = |x-2| + |x-3| + |x+1| Since you asked no questions about it, nor provided the division of the domain among the parts, I'll just present ...
June 1, 2015

DISCRETE MATH
(a) clearly 2R4 and 2R6. for a function, the each m must be related to a single n (b) A is the set of factors of 52. I'm sure you can list them. (c) B is the set of all multiples of 52. (d) A ∩ B = {52}
May 31, 2015

Physics
since we cannot see the diagram, you will have to describe the series/parallel connections. Also, you have not asked a question. I assume you want the voltage drop across r.
May 31, 2015

Math
1600-1500 = 100 So, that is 100/150 = 0.67 std above the mean.
May 31, 2015

Math
enter your numbers on this web page and you can see that the answer is 82% http://davidmlane.com/hyperstat/z_table.html If you play around with things a bit, it should make things clearer.
May 31, 2015

geometry
we want AD parallel to BC, so D will have to be (x,-1). Since (10,-1) is 2 units to the right of B, D will have to be 2 units to the left of C: (-3,-1)
May 31, 2015

Algebra
since time = distance/speed, if the wind has speed w, 600/(100+w) = 400/(100-w) Now just find w.
May 31, 2015

Sequences
Find the ratio of the 1st two terms: (4/27) / (8/81) = 4/27 * 81/8 = 3/2 You can easily verify that each term is 3/2 the previous one. So, So, a10 = 8/81 * (3/2)^9 = 2^3/3^4 * 3^9/2^9 = 3^5/2^6 = 243/64
May 31, 2015

Math
if there are a lbs of A, then the rest (174-a) is B. So, 5.85a + 4.40(174-a) = 906.25
May 31, 2015

Math
if we set the wave with its vertex at (0,30) and it has height 0 at x=-20 and 20. y = 30-ax^2 y(20) = 0, so 30/400 = a = 0.075 y = 30 - .075x^2 Now we want to know where y > 10: 30 - .075x^2 > 10 20 > .075x^2 -16.32 < x < 16.32 So, to travel a distance of 32.64m...
May 31, 2015

DISCRETE MATH
because 3*4 = 12 = 2 (mod 5)
May 31, 2015

Math
as usual, draw a diagram. You will see that tanθ = 120/313
May 31, 2015

Logs
I assume sqrt4(n) means 4th root. So, log 4throot(x^16/y^4) = log(x^4/y) = 4logx - logy = 4*8 - 1 = 31 Of course, you could have worked it without extracting the 4th root: log 4throot(x^16/y^4) = 1/4 log(x^16/y^4) = 1/4 (16logx - 4logy) = 1/4 (16*8-4*1) = 1/4 (128-4) = 1/4 * ...
May 31, 2015

Trigonometry
sinθ = 20/130
May 31, 2015

math
the mean of two values lies between them. So, (√2+√3)/2 does the job. Or, just note that √2 = 1.414... √3 = 1.732... Now pick any value in between them.
May 31, 2015

math
I assume you want to solve for a and b in (√2+√3)/(3√2-2√3) = a+b√6 get rid of the radicals in the bottom by recalling that (x-y)(x+y) = x^2-y^2. So, multiply top and bottom by 3√2+2√3 and you have (√2+√3)(3√2+2√...
May 31, 2015

Calculus
just use the power rule: A' = 2x - 128/x^2 A" = 2 + 256/x^3
May 31, 2015

physics
you want mass. So, since density = g/cm^3, you need to multiply density times volume to get mass. So, do the math...
May 31, 2015

geometry
on the vertical line x=7, you could have (7+55,-2) or (7-58,-2) On the horizontal line y = -2, you could have (7,-2+59) or (7,-2-51) Of course, you could pick any points on the circle (x-7)^2 + (y+2)^2 = r^2 where r is between 50 and 60.
May 31, 2015

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