Thursday

September 18, 2014

September 18, 2014

Total # Posts: 25,050

**pre-calculus**

If there are x lamps, then 54x = 3564 So, there are 66 lamps sold If they cost c each, then 66c + 396 = 3564 So, the cost is 48. So, for 145 lamps, the profit is 145*(54-48) - 396 = 474
*September 15, 2014*

**Grade 11 Math functions**

All polynomials have domain xeR. All reals. Your domain makes no sense. xeR includes all values, including 2<x<3. Since y = (x - 5/2)^2 - 1/4, its minimum is at y = -1/4. So, the range is all reals y >= -1/4.
*September 15, 2014*

**geometry**

since the median is the middle value, the probability is 1/2 that a random value is above or below the median.
*September 15, 2014*

**math**

how long does it take to land? 9.8 - 4.9t^2 = 0 Now, with that t, how far does he go at 15.2 m/s? That would be 15.2 t
*September 15, 2014*

**algibra1**

If the 2nd side is x, then 2x + x + x+4 = 24 Now just find x, which is the 2nd side. Then it is easy to figure the other two sides.
*September 15, 2014*

**Pre-Calculus/Trigonometry**

correct
*September 15, 2014*

**Math**

use the law of cosines: d^2 = 18^2 + 11^2 - 2(18)(11)cos 70°
*September 15, 2014*

**Math**

actually, 711,311 is the only answer. If the hundreds digit is 3, then the remaining 4 digits must add to 4. They must all be 1's.
*September 15, 2014*

**dav**

the area scales as the square of the sides, so the sides are in the ratio √15/√25
*September 15, 2014*

**Math**

B clearly not, since 1+1=2, which is not in B T clearly, since adding any two multiples of 4 yields another multiple of 4. F yes, since adding any two integers yields another integer greater than 4. No idea. What is W?
*September 15, 2014*

**algebra**

If x is invested at 9%, then .068(4600) + .09(x) = .08(4600+x)
*September 15, 2014*

**algebra**

If x is drained, then .25(6-x) + 1.00(x) = .33(6)
*September 15, 2014*

**algebra**

if we call x the flying time for the 2nd plane, then since distance = speed * time, 660x + 540(x+1) = 1800 x = 1.05 hours So, how far did the first plane travel in 2.05 hours?
*September 15, 2014*

**Math 221**

(a) looks to me like it will be (30/110)(29/109)(28/108) Do (b) similarly. This is just like the problems involving drawing from a deck of cards.
*September 15, 2014*

**Math**

do the graphs at wolframalpha.com match your own? There, the two lines are clearly reflections in the x-axis.
*September 15, 2014*

**Math**

to reflect over the x-axis, y values change sign. So, f(x) -> -f(x), so it is -f(x) = 3x-5 Note that -f(-x) = -(-3(-x)+5) = -(3x+5) = -3x-5 See the reflection at http://www.wolframalpha.com/input/?i=plot+y%3D-3x%2B5%2C+y%3D3x-5
*September 15, 2014*

**algebra**

No sweat. Getting from the words to the algebra is half the battle. Do lots of word problems. They help you think mathematically.
*September 15, 2014*

**algebra**

If the cost is x, then x/4 = x/3 - 4000
*September 15, 2014*

**algebra**

I'll do one; you try the others. If you get stuck, come on back and show where. 5/13 t = -9 multiply by 13/5 to cancel the 5/13: t = -9(13/5) t = -117/5 I suspect #3 has a typo
*September 15, 2014*

**Algebra**

I think the easiest way is to use the point-slope form of the equation, since they gave you a point and a slope. Recall that the equation for a line through (h,k) with slope m is y-k = m(x-h) So, you have y+3 = -2(x+1) Now work with that: y+3 = -2x-2 y = -2x-5
*September 15, 2014*

**calculus**

(a) the period of sin(kt) is 2π/k, so we have period 2π/π = 2 seconds. (b) since the minimum of sin(kt) = -1, our minimum is -3/5 (c) since the length of the rod is 1, x^2+y^2 = 1 That means that y^2 = 1/25 (16 + 9cos^2(πt)) when x = 3/10, t=1/6, y = √...
*September 15, 2014*

**Maths**

since most bridges are level, I find the term questionable. I expect that in such problems, we're talking about the apex of the supporting structure, which is often a parabola. That would then be the vertex of the parabola.
*September 15, 2014*

**pre calc**

If x oz. of gold, we have 6000x + 50(1-x) = 200
*September 15, 2014*

**Pre Calc**

If normally the speed is x, then 90/x = 1 + 90/(x+3)
*September 15, 2014*

**Pre Calculus**

If the speed is x, then since time = distance/speed, 48/(x+4) = 32/(x-4)
*September 15, 2014*

**math**

Hint: Draw a diagram. You should recall that a common right triangle with integer sides is 7-24-25.
*September 14, 2014*

**AP Calculus**

You have y' = (2x-y)/(x-2y) at x = -2, y = -1±√13, so there will be two lines tangent to the ellipse at x = -2. for y = -1+√13, y' = (-4+1-√13)/(-2-2(-1+√13)) = (-3-√13)/(-2√13) = (13+3√13)/26 So, the line is y = (13+3&#...
*September 14, 2014*

**Algebra**

c+7 <= 3 c <= -4 So, plot a dot at -4 and shade everything to the left.
*September 14, 2014*

**Math**

since there are 10 choices for each digit, that would mean there are 10^7 possible numbers. Actually, SS numbers have 9 digits.
*September 14, 2014*

**Math**

Since there are 2 choices for each answer, there are 2^6 = 64 ways to answer all the questions. If some may be left unanswered, then we have 2^6 * 6C6 ways to select and answer all 6 2^5 * 6C5 ways to select and answer 5 2^4 * 6C4 ways to select and answer 4 and so on. Adding ...
*September 14, 2014*

**algebra**

just plug in either of the points. They must satisfy the equation, so if we pick (-8,-10), (-8+1.5)^2 + (-10+7)^2 = r^2
*September 14, 2014*

**algebra**

We need to rearrange terms into the standard equation: 5x^2−6x+5y^2+8y−9=0 5(x^2 - 6/5 x) + 5(y^2 + 8/5 y) = 9 (x^2 - 6/5 x + 9/25) + (y^2 + 8/5 y + 16/25) = 9/5 + 9/25 + 16/25 (x - 3/5)^2 + (y + 4/5)^2 = 70/25 Now you can read off the desired data.
*September 14, 2014*

**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*

Pages: <<Prev | 1 | **2** | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | Next>>