Wednesday

October 22, 2014

October 22, 2014

Total # Posts: 25,978

**Algebra**

(7/2)^2 (18/2)^2 (√64)*2 (√49/4)*2 Note that (a) and (d) are the same polynomial
*September 13, 2014*

**Law of Cosines**

Hmmm. Look at triangle CBD. You know all three sides now, so 14^2 = 13.3^2 + 12^2 - 2*13.3*12 cos CBD Now you have ABC = ABD+DBC Now use law of cosines again to get AC.
*September 13, 2014*

**math**

If thrown with the same initial velocity, and you ignore air resistance, they will all achieve the same maximum height.
*September 13, 2014*

**Pre-Calculus**

#1: I get -2/-7 = 2/7 #2: Nope. Parallel lines have the same slope. #3: slopes are -1/2 and 1 Neither
*September 13, 2014*

**Math**

C y" + (y')^2 + y^3 = f(x) is a 2nd order equation. You have to integrate twice to get y, and that introduces two constants. It is a 3rd-degree equation, because of y^3 Doesn't matter how many derivatives are present. Just their order. Better review DE's. Here...
*September 13, 2014*

**science**

of course. Not likely, though, imo.
*September 13, 2014*

**still confused**

well, you know the length is 2w-3, and you know w=25, so what's the trouble?
*September 12, 2014*

**Algebra**

AHA! My mistake. 24/6=4, not 6. Granted I was wrong, you should have caught my error and noted it, rather than just saying we disagreed.
*September 12, 2014*

**Algebra**

I showed my work. Why not show yours? Maybe we can come to some agreement...
*September 12, 2014*

**Algebra**

The result of each step is shown below: x 2x (2x)(3) = 6x 6x+24 x+6 6 The result is always 6
*September 12, 2014*

**Physics**

In x-y coordinates, A = (2.62,0) B = (0,2.26) C = (-1.4,0) D = (0,-2.8) A+B+C+D = (1.22,-0.54) That is 1.33 at E23.88°S
*September 12, 2014*

**Math(Geometry) beware its hard for sixth graders!**

Nice table, but you just need to understand the definition of the trig functions. In this case, h/19 = sin 42º h = 19*.6691 = 12.71 You should have immediately seen that your answer is wrong, because the ladder is only 19 feet long. How could it possibly reach 21 feet up ...
*September 12, 2014*

**Math**

the planes are approaching at 520+620=1140 mph By the time the 2nd plane takes off, the distance between the planes is only 1800-520=1280 miles At those speeds, they cover the distance in 1280/1140 = 1.123 hours I expect you can now answer the question.
*September 12, 2014*

**Math**

If $x at 4%, then .04x + .025(14000-x) = 458
*September 12, 2014*

**math**

If there are x with stripe only y with dot only z with stripe and dot, z = 6 (x+z) = 3y 3(y+z) = 2x So, x+y+z = 40
*September 12, 2014*

**Algebra**

minimum cost is at the vertex of the parabola, which occurs at x = 8/(2/5) = 20
*September 12, 2014*

**Mathematica**

or, convert to have the same denominator. 1/3 = 5/15 3/5 = 9/15 9 is 5+4, or 80% more than 5
*September 12, 2014*

**Math**

(a) recall that the vertex occurs at t = -b/2a = 20/32 = 5/8 So, figure h(5/8) (b) solve for t when h=0 (c) the point where he lands is a root of the function. h(t) = 0
*September 12, 2014*

**Math**

Looks like y = -|x^3| or y = -|x|^3 Not sure what the parent function would be. |x|^3 I guess, if all modifications to be considered are linear transformations.
*September 12, 2014*

**Algebra**

only if a=b
*September 12, 2014*

**MATH**

Base b only needs b symbols. After all b are used up, the next number is 10, and the bottom digit cycles through the other b-1 digits again, before going on to 20 (assuming b >= 2!)
*September 12, 2014*

**algebra**

T F (-2)^2 = 2^2 T
*September 12, 2014*

**algebra**

1 < 3x+2 < 12 subtract 2: -1 < 3x < 10 divide by 3: -1/3 < x < 10/3
*September 12, 2014*

**Pre-Calculus/Trigonometry**

Not A. It charges double for minutes over 250 Not B. flat rate up till x=250 Not C. Drops the $29 for x>250 Clearly D. Only charges the .35 for those minutes over 250.
*September 12, 2014*

**Algebra**

PI, not pie! v = pi r^2 h + 2/3 pi r^3 So, given the numbers above, pi (225) h + 2/3 pi (3375) = 10800 pi h = (10800pi - 2250 pi)/(225pi) = 38
*September 12, 2014*

**maths**

a=2 For details using elimination, see http://www.gregthatcher.com/Mathematics/GaussJordan.aspx
*September 12, 2014*

**trigonometry - kindly help, needed badly**

Draw a diagram, looking along the stream. If the width of the stream is w, and the height of the tree is h, then h/w = tan38°23' h/(w+200.6) = tan20°22' Eliminating w, we have h*cot38°23' = h*cot20°22' - 200.6 h = 200.6/(cot20°22' - ...
*September 12, 2014*

**Math**

Ahem 2 = Ab^-1 = A/b, so A = 2b 1 = Ab^3 = 2b^4 b = (1/2)^1/4 2 = A*2^(1/4) A = 2^(3/4) y = 2^(3/4) (1/2)^(x/4) or y = ∜(8/2^x)
*September 12, 2014*

**Grade 9 Math**

-(w^2 - 60w + 900) + 80w + 600 -w^2 + 60w - 900 + 80w + 600 -w^2 + 140w - 300
*September 12, 2014*

**Algebra Grade 10**

If we place the vertex at (0,2), then y = 2-ax^2 Since the span is 5 meters, the roots are at x = ±5/2 So, 2 - 25/4 a = 0 a = 8/25 y = 2 - 0.32x^2
*September 12, 2014*

**Math Problem (please help)**

How about 2(6*3)+2w = 36+2w
*September 12, 2014*

**Math 112**

I say see the related questions below and look at the response I posted yesterday.
*September 12, 2014*

**Maths**

consecutive angles are supplementary, so the angles are 44,136,44,136
*September 12, 2014*

**Math**

If 60% were boys, the ratio of boys:girls = 3:2 So, b/(b-1) = 3/2 2b = 3b-3 b = 3 So, 3 boys, 2 girls 60% boys
*September 12, 2014*

**Algebra**

(116 1/4) / (3 3/4) = 31
*September 12, 2014*

**Math Problem (please help)**

9x^3 - 30x^2 + 37x - 26 = 0 A little poking around with synthetic division show that f(x) = (x-2)(9x^2-12x+13) So, the only real root is x=2
*September 12, 2014*

**Math Problem (please help)**

Just solve -35x^3 + 2500x^2 - 275000 = 850000 using your favorite numeric method, or a graphing utility such as http://www.wolframalpha.com/input/?i=-35x^3+%2B+2500x^2+-+275000+%3D+850000
*September 12, 2014*

**math**

having no diagrams to consider, I'd say you did not explain anything well enough.
*September 11, 2014*

**Math**

any number between 0 and 2
*September 11, 2014*

**Math**

.00006 = 6*10^-5 I'd round up to 10^-4 789000 is almost a million, or 10^6 It is 7.89*10^5, so it rounds up to 1.0*10^6
*September 11, 2014*

**algebra**

anders-carmen = (anders-kaye) + (kaye-carmen) = 4.89 + 10 = 14.89 Rearranging things a bit, we are told Carmen finished 10 seconds before Kaye Kaye finished 4.89 seconds before Anders. alicia and donna are just noise.
*September 11, 2014*

**math**

h(t) = 51.6 - 4.9t^2 we want the time between when h(t) = 15.7 and h(t) = 1.90 So, just solve for t in 51.6-4.9t^2 = 15.7 51.6-4.9t^2 = 1.90 and subtract to find how long it will take to crush the man's skull.
*September 11, 2014*

**college math**

OK, v = 1/3 π r^2 h so, what? 3v = πr^2 h h = 3v / πr^2
*September 11, 2014*

**college math**

if x liters evaporate, the salt content remains the same, so .12(110) = .20(110-x) Now just solve for x.
*September 11, 2014*

**college math**

since distance = time*speed, 11x = 10(4.2-x) x = 2 So, the boat's speed is 2 knots. I expect now you can figure the distance.
*September 11, 2014*

**Geometry**

Nope. LM cannot be the midpoint of LM. If N is the midpoint of LM, then LN is half of LM, so 3x+5 = 2(5x+40) 3x+5 = 10x + 80 7x = -75 that makes the lengths negative. So, we must have M is the midpoint of LN. In that case, 5x+40 = 2(3x+5) 5x+40 = 6x + 10 x = 30 So, LM=MN=95 ...
*September 11, 2014*

**math**

#1: naturally, (1/4)/39.35 hours time = distance/speed
*September 11, 2014*

**Magic Square**

The sum of all the numbers is 99, so each row must sum to 33 10+11+12 = 33, so maybe that will form a diagonal. A little playing around, placing 19,20,21 in different rows and columns, gave me 19 3 11 2 10 21 12 20 1
*September 11, 2014*

**math**

p = r+4 6(r+4) + 8r = 38 So, solve for r and then figure p.
*September 11, 2014*

**Differential Equations**

Evidently you have not reviewed the definition of a linear DE: A differential equation is linear if the unknown function and its derivatives appear to the power 1 (products of the unknown function and its derivatives are not allowed) and nonlinear otherwise. So, the first ...
*September 11, 2014*

**math**

Hard to say. What is x supposed to represent? Any of the selections could be correct, depending on what x is.
*September 11, 2014*

**geometry**

For x, -9 is 8 below -1 So, the other end is 8 below -9, or -17 Same for y. The other problem is the same method.
*September 11, 2014*

**Math**

Geez. We can, without loss of generality assume that a < b, so since the parabola opens upward, it dips below the x-axis between the roots. Naturally, it changes signs at a and b. UNLESS a=b In that case, there is a single root, and the polynomial does not change sign, as ...
*September 11, 2014*

**Math**

clearly the polynomial is zero if any of its factor is zero. So, one value of x is where x-a=0, os x=a I expect you can find the other.
*September 11, 2014*

**Algebra 1**

88-7.5 <= x <= 88+7.5
*September 11, 2014*

**math**

19:7 > 7:26
*September 11, 2014*

**math**

what "result" must be 6 digits? x+y+z = 39 y = z/2 x = z-1 x=15 y=8 z=16
*September 11, 2014*

**Calculus II**

Looks good to me. I'd have just written 9/√51, but some folks get itchy over radicals in the denominator.
*September 11, 2014*

**math**

the planes are approaching at 520+620=1140 mph By the time the 2nd plane takes off, the distance between the planes is only 1800-520=1280 miles At those speeds, they cover the distance in 1280/1140 = 1.123 hours I expect you can now answer the question.
*September 11, 2014*

**math**

since time = distance/speed, d/4 + d/2 = 126 Now just solve for d
*September 11, 2014*

**math**

If $x at 4%, then .04x + .025(14000-x) = 458
*September 11, 2014*

**math**

The new machine completes 2/13 of the job. So, the older machine requires (11/13)/(1/15) = 12.7 hours to do the rest.
*September 11, 2014*

**math**

Hmmm. I may have been hasty. Anyway, if there are x oz. of $3.50 alloy, the rest (30-x) is the $7.00 alloy. So, check to be sure that the value of silver adds up: 3.50x + 7.00(30-x) = 6.30(30) x = 6
*September 11, 2014*

**math**

we've done a lot of these mixture problems for you. Why not try some yourself, and we can check your work...
*September 11, 2014*

**Math**

Do you not see that you are missing some data here?
*September 11, 2014*

**math**

Tell you what. I'll solve one, and you can try the others. Post your work if you get stuck. x^2-3(2x+3)=0 x^2-6x-9 = 0 x = (6±√(36+36))/2 = (6±6√2)/2 = 3±3√2
*September 11, 2014*

**Grade 10 Maths**

recall that the vertex of a parabola is at x = -b/2a In this problem, that is x = -20/-1 = 20
*September 11, 2014*

**1**

First, find the speed of sound, and then recall that distance = time * speed. Then, since time = distance/speed, divide that distance by the speed of light.
*September 11, 2014*

**Year 10 Alegbra**

A = 8w - 2w^2 As you recall, the vertex of a parabola (in this case, the maximum area) is achieved at x = -b/2a In this case, that's x = -8/-4 = 2 Or, you can note that the roots of A=0 are 0 and 4. The vertex is midway between the roots, at x=2.
*September 11, 2014*

**Year 10 Alegbra**

depends on what the question is, no?
*September 11, 2014*

**math**

so, you gonna share those roots with us?
*September 11, 2014*

**Math: pre calculus**

If the width of the pens is x, and the overall length is y, then 3x+y = 240 The area is a = xy = x(240-3x) = 240x - 3x^2 This is just a parabola, with vertex at x = 40 So, the pens are each 40 by 60 ft. As usual, maximum area is achieved when the available fence is divided ...
*September 11, 2014*

**mathematics**

just as x^a * x^b = x^(a+b) log(a*b) = log(a) + log(b)
*September 11, 2014*

**MATH**

ummm, 53x5 = 265
*September 11, 2014*

**Force of Gravity**

since F = GMm/r^2 when r doubles you have GMm/(2r)^2 = Gmm/4r^2 = GMm/r^2 * 1/4 = F/4
*September 11, 2014*

**Geometry**

we have if p then q we are told p is true, so therefore, q: the measure is 90 degrees.
*September 11, 2014*

**8th Grade math**

False who says they have to be spaced 1 degree apart? If they are spaced 1 minute apart, there are 60*360 = 21,600 rays
*September 11, 2014*

**Quantitative Reasoning (math)**

360/60 = 6
*September 11, 2014*

**8th grade math**

Nope.
*September 11, 2014*

**8th grade math**

False. Between any two points there is another. Following that reasoning, between any two points there are infinitely many others.
*September 11, 2014*

**Math**

The 10x10 cake is 5x5 pieces, so it takes 4+4=8 cuts to do the job. That is 5 seconds per cut. The 12x12 cake is 6x6 pieces, so it will take 5+5=10 cuts, or 50 seconds. Assuming a 12" cut can be made in the same time as a 10" cut!
*September 10, 2014*

**Math**

If the original selling price was s, then she paid 3*s(1-.20)+10
*September 10, 2014*

**Math**

If there were originally b boys out of s students in the class, b/s = 2/3 b/(s+2) = 3/5 Or, b = 2s/3 5b = 3s+6 So, 5(2s/3) = 3s+6 10s = 9s+18 s = 18 Now you should be able to answer the question.
*September 10, 2014*

**pre calculus**

You know that a parabola with vertex at (h,k) is y = a(x-h)+k So, we now have y = a(x+3) - 10 Now just plug in (2,-5) to find a.
*September 10, 2014*

**Geometry**

Now you know that RSP = PST = -17 So, since RST = RSP + PST, RST = -34 Not sure what the negative values indicate. Sure there's not a typo in the problem?
*September 10, 2014*

**Geometry**

Use your distance formula: AB = √((2-0)^2+(7-3)^2) = √(4+16) = √20 = 2√5
*September 10, 2014*

**math**

Actually, the volume of a cone is v = 1/3 π r^2 h
*September 10, 2014*

**math**

2(w + 2w-3) = 144
*September 10, 2014*

**Math**

1,2,3,4,5,6,7,8,9,10,11,12,13 add up to 91. So, it looks like we have 1,2,3,4,5,6,7,8,9,10,11,12,14
*September 10, 2014*

**math**

Not quite sure what you're doing there. If a side of the square is 45, its perimeter is 180. Thus, the perimeter of the triangle is 90. So, each side of the triangle must be 30.
*September 10, 2014*

**algebra 1**

If x >= 0, |x| = x If x < 0, |x| = -x So, from what we have above, x >= 0 x-2 < 0, or x < 2 So, 0 <= x < 2
*September 10, 2014*

**Trig**

If the nearer observer is at distance x from the obelisk, then we have h/x = tan 65° h/(x+25) = tan 44° so, eliminating x, just solve for h in h/tan65° = h/tan44° - 25 h = 25/(cot44°-cot65°)
*September 10, 2014*

**math**

400m / 92s = 4.35 m/s or, 400m / 1.533 min = 260.9 m/min
*September 10, 2014*

**college algebra**

If x oz. of 1% are used, then the rest (3-x) are 5%, so .01x + .05(3-x) = .04(3) x = 3/4 So, 3/4 oz of 1% and 9/4 oz of 5% Note that 4% is 3/4 of the way from 1% to 5%, so 3/4 of the total is the 5% strength.
*September 10, 2014*

**college algebra**

If x is at 8%, the remainder (22000-x) is at 6% so, .08x + .06(22000-x) = 1680 ...
*September 10, 2014*

**math**

just plug in your numbers: h(t) = -16t^2 + 84t + 60 assuming he kicks it straight up. Now just plug in t=2
*September 10, 2014*

**Math**

Since A+B+C=180, C=94.24 So, using the law of sines, c/sinC = a/sinA Now just plug and chug.
*September 10, 2014*

**Algebra!!!! HELP**

Since F=kx, F/x is constant. So, (a) 120/x = 265/0.15 (b) F/0.3 = 265/0.15 Note that you can answer these questions without even determining the value of k explicitly.
*September 10, 2014*

**math**

Just use the quadratic formula: x = (-(c-a)±√((c-a)^2 - 4(b-c)(a-b)))/(2(b-c)) You can play around with that some, but I don't see much in the way of simplification. http://www.wolframalpha.com/input/?i=%28b-c%29x%C2%B2+%2B+%28c-a%29x+%2B+%28a-b%29
*September 10, 2014*

Pages: <<Prev | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | **12** | 13 | 14 | 15 | 16 | 17 | 18 | Next>>