Wednesday

October 1, 2014

October 1, 2014

Total # Posts: 25,393

**Pre-Calculus**

start with point-slope form: y+3 = -2(x+1) Now just rearrange terms to the form you want.
*September 14, 2014*

**Algebra**

since time = distance/speed d/18 + d/10 = 14 d = 90 5 hours out, 9 hours back = 14 total
*September 14, 2014*

**math**

since cos 60.0˚ = 1/2, it has gone 24 km. 24km/1min = 24 km/min
*September 14, 2014*

**Math**

(2x-9)log7 = (2x)log4 2x log7 - 2x log4 = 9log7 x = 9log7/(2log7-2log4) There are, of course other ways of expressing those log terms...
*September 14, 2014*

**trig - eh?**

"3acos^2x.sin" means what?
*September 14, 2014*

**trig - eh?**

what does "a" have to do with anything?
*September 14, 2014*

**Maths**

80000/20000 = 4 so you want the time to grow by a factor of 4: (1+.10/12)^(12t) = 4 Now just solve for t.
*September 14, 2014*

**Pre-Calculus**

clearly you have x(x^2-x+1) Only one real root, of multiplicity 1. Two complex roots, also of multiplicity 1.
*September 14, 2014*

**geometry**

no ideas at all? Better review the topic and come on back with your choices. We can check for accuracy.
*September 13, 2014*

**Math Proof**

rational (x+y)/2 irrational: (x+y)/2 + √2/10^21
*September 13, 2014*

**Go with Damon**

Oops. My bad. Didn't set things up correctly.
*September 13, 2014*

**math (create equation)**

Or, 2 by 40
*September 13, 2014*

**math (create equation)**

Looks like 3 plots, each of width x and height y. So, 4x+2y = 88 xy = 80 x(44-2x) = 80 2x^2-44x+80 = 0 x^2-22x+40 = 0 (x-20)(x-2) = 0 x = 20 So, each plot is 20 by 4
*September 13, 2014*

**trig**

your calculator probably has a yellow or blue button which makes the sin function do arcsin instead. You want arcsin(.322)
*September 13, 2014*

**math (create equation)**

In terms of minutes taken. b = 2a c = 3a 1/a + 1/2a + 1/3a = 1/60 a = 110
*September 13, 2014*

**math**

dividing by 10 shifts the decimal point to the left. That puts the zero after the decimal point, effectively erasing it. Or, if the number ends in zero, it has the form N0 = N(10) So, dividing by 10 gives N(10)/10 and the 10's cancel, leaving just N (the number without the...
*September 13, 2014*

**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*

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