Sunday
September 21, 2014

Posts by Steve


Total # Posts: 25,114

algebra
domain: x >= 0 range: y >= 16
September 14, 2014

Math
If the original width is x length is 2x With a=2, our new box has volume (a)(x-2a)(2x-2a) = 32 2(x-4)(2x-4) = 32 2(x-4)(2x-4) - 32 = 0 4x(x-6) = 0 x = 6 So a sheet 6x12 will be cut to a box 2x2x8 with volume = 32
September 14, 2014

Physics !!!!!!!!!!!!!!!!
v(t) = Vo + at where a is negative, in this case. s(t) = Xo + Vot + 1/2 at^2 where a is negative If all you wanted was the formulas, why not just look in your text book? They are presented there. I'm sure.
September 14, 2014

Limits
1/(3+x) -> 1/3 1/(3x) -> ∞ clearly the sum is ∞ However, the left and right limits have opposite signs.
September 14, 2014

PLEASE HELP! Math
Liz is going 6 mi/hr faster than Mandy. By the time she starts, Mandy has gone (1/3)(30) = 10 miles So, at 6 mi/hr, it will take 10/6 = 1 hr 40 min to catch up with Liz. So, that will be 2 hours after Mandy started, or 1:00 pm. Or, you can plot both cyclists' positions as ...
September 14, 2014

Math
since each card has a 1/52 chance of being drawn, that would be (1/52)^12
September 14, 2014

math
75*42*(1/3) ft^3 * 7.5gal/ft^3 = 7875 gal
September 14, 2014

Geography?
Don't see much geometry in that ...
September 14, 2014

Algebra 1
start off with the point-slope form, since that is what they gave you: y+3 = -2(x+1) and rearrange things to fit the slope-intercept form.
September 14, 2014

math
well, just solve for x in -0.01x^2 + 130x - 180000 = 174900 x = 3900 or 9100
September 14, 2014

AP CALC. AB
#1: when is the denominator zero? When 1+sinx = 0 sinx = -1 x = 3π/2 + 2kπ Since f(-5) > 0 and f(-1) < 0, f(x)=0 only for a single value of x between -5 and -1. I assume the given choices included such a number.
September 14, 2014

math
2000000cm / (65π cm/rev) = 979.4 rev
September 14, 2014

algebra
Assuming you want to solve for x, x^2+x-1 = 0 looks like you need the quadratic formula. See http://www.wolframalpha.com/input/?i=x2+%3D+%E2%88%92x+%2B+1
September 14, 2014

algebra
(z-1)^2 = -4 z-1 = ±2i z = 1±2i
September 14, 2014

algebra
just solve -16t^2 + 200t = 380 -16t^2 + 200t - 380 = 0 Now just use the quadratic formula to find the roots.
September 14, 2014

Pre-Calculus
clearly, one such P(x) = (x-(2+i))(x-(2-i)) = ((x-2)-i)((x-2)+i) = (x-2)^2 - i^2 = x^2-4x+4 + 1 = x^2-4x+5 extra credit: why does the question imply that there is more than one such P(x)?
September 14, 2014

physics
it's probably easiest to find out how long it takes, then recall that v = at. So, if we have the car start the race at t=0, x=0, 35t + 3/2 t^2 = 48+24t t = 3.07 so, v = 3*3.07 = 9.21 m/s
September 14, 2014

Math
If the three E's are together, you might as well just count them as a single letter. So, there are just 6! ways to arrange the letters. Your 5!*6 is the same value. I assume you considered the 5! permutations of BRKLY times the 6 places you could stick the E's.
September 14, 2014

Dang!
Forgot the division step. Sorry.
September 14, 2014

8th grade homework
the value after each step is shown below. x x-6 10+x-6=30 so, x+4=30 x=26
September 14, 2014

physic
Just plug in your values and solve for y=0 in the equation of motion: y = 15 + x tanθ - g/(2(v cosθ)^2) x^2
September 14, 2014

maths
(1+5r) = 1.6 5r = .6 r = .12 or 12%
September 14, 2014

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

Math
2=2
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

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