Wednesday
September 17, 2014

Posts by STEVE


Total # Posts: 25,003

Math
Nope. Forgot the 60 degree angle. In that case, recall that cos 60 = 1/2
September 17, 2014

Math
Hint: Think of the ubiquitous 3-4-5 right triangle, scaled up to 6-8-10.
September 17, 2014

n2maths
50^2 + x^2 = (x+10)^2
September 17, 2014

Math
It appears that the two boys are less than 10, since adding up all the ages gives only 83 Granny cannot be less than 83-17=66 66+8+9=83 67+7+9=83 68+6+9=68+7+8=83 69+5+9=69+6+8=83 71+5+7=83 72+4+7=72+3+8=72+2+9=83 73+3+7=83 WE HAVE A WINNER!
September 17, 2014

maths
having what as 5000m?
September 17, 2014

Algebra
correct both times. In general, for a given set of problems, U is the Universe. Any subsets being discussed will always be subsets of U, or things are poorly set up.
September 17, 2014

Algebra
so, use one. wolframalpha.com does a good job
September 17, 2014

math
We have two lines, with slopes (-5-b)/10 and (-3)/(-6-a) If the lines are perpendicular, then (-5-b)/10 * (-3)/(-6-a) = -1 (b+5) = 10/3 (a+6) b = 5/3 (2a+9)
September 17, 2014

Math
We have a=7 d=12 So, when does Tn exceed 1000? Tn = 7+12(n-1) = 12n-5 12n-5 < 1000 12n < 1005 n < 83.75 So, the first 83 terms are less than 1000 Similarly for 2000
September 16, 2014

Math
clearly, a = 28 r = 1/6 So, S = a/(1-r) = 28/(5/6) = 33.6
September 16, 2014

Math
since x has an unspecified value, there is no way to round it. So, I assume you want to solve the equation, and round the answer to two decimals. 2x^4+3x-4 = 0 There are only two real roots, x = -1.43 or 0.90 The graph is at http://www.wolframalpha.com/input/?i=2x^4%2B3x-4 Or...
September 16, 2014

math
16/10 is the same as 1.6
September 16, 2014

math
probably because you have learned by heart some simple results, like sums totaling 10, or 5, etc. The mechanics never change, so if some are easier, it just means that you have learned some patterns that you can recognize.
September 16, 2014

math
The language is very confusing in its use of present and past tenses. When is "now"? The end of the year? If girls joined the band, how come there are now fewer students than at the beginning? I cannot believe the question was posed as you state. If so, the problem ...
September 16, 2014

trigo
First, vessels travel on headings, not bearings. 200 @ 245° = (-181.262,-84.524) 50 @ 320° = (-32.134,38.302) add them up to get (-213.396,-46.222) = 218 @ 258°
September 16, 2014

Algebra
correct.
September 16, 2014

Calculus
f(a) = 3a^2-2a f(a+h) = 3(a+h)^2 - 2(a+h) = 3a^2 + 6ah + 3h^2 - 2a - 2h f(a+h)-f(a) = 6ah + 3h^2 + 2h So, (f(a+h)-f(a))/h = 6a + 3h + 2 So, with various values of h, f(a+1) = 6a+3+2 f(a+0.1) = 6a + 0.3 + 2 = 6a + 2.03 and so on. Nothing difficult, just algebra I.
September 16, 2014

Math
That's a lot of work. Just think about it a bit. You start with 1 gram. 3 days later the amount left is 0.1 gram If the half life is k days, then (1/2)^3k = 1/10 3k = log(.1)/log(.5) = 3.32 So, k = 1.11 R(t) = (1/2)^(1.11t) But, since we like things base e for our ...
September 16, 2014

Math
just solve for x in the equation −0.01x2 + 130x − 180,000 = 174900
September 16, 2014

math
The expression factors as (3x-1)(x+2) However, there are lots of other ways to divide things up. For example, if x=3, the area is 8*5 = 40, but those are not the only two ways to get two numbers which multiply to 40.
September 16, 2014

math help
Just plug in the value: (4x+8)(x+2)(2x+4) / 2((4x+8)(x+2)+(4x+8)(2x+4)+(x+2)(2x+4)) = 8(x+2)^3 / 28(x+2)^2 = 2(x+2)/7
September 16, 2014

Math
steps to what?
September 16, 2014

math
The answer is r^2-5 + 5/(r^2-2) See the details when you enter your polynomials at calc101.com. Click on the long division button.
September 16, 2014

Math
after n hours, the length is 3*3^(n-1) = 3^n Now just plug in n=3
September 16, 2014

math
since the circumference is 8*3.14, the diameter is 8
September 16, 2014

math
f = m+5 f+5 = 2m m+5 + 5 = 2m m = 5
September 16, 2014

math
the first car went 20 miles before the 2nd car started out. So, it made up 20mi/(5/3 hr) = 12 mi/hr That is, car 2 was going 12 mi/hr faster than car 1, or 72 mi/hr Check: car 1 went 120 miles in 2 hours car 2 went 72(5/3) = 120 miles in 1 hr 40 min
September 16, 2014

Algebra
g(f(x)) = {g(8),g(5),g(-5),g(3)} = {10,9,3} g(3) is undefined
September 16, 2014

Algebra 2
y = 2x-1 + 3/5
September 16, 2014

Algebra 1
your solution is correct. To check on (180,-30), plug it in 8(180)+5(-30) =?= 900 But, how do you sell -30 student tickets?
September 16, 2014

Math
(a) max height occurs at t = -87/-32 (b) just solve for t when h=0
September 16, 2014

Trig
if the wind speed is w and the plane's speed is s, then (w cos-135°,w sin-135°)+(s cos63°, s sin63°) = (550 cos64°,550 sin64°) -.707w + .454s = 241.104 -.707w + .891s = 494.337 w = 31.089
September 16, 2014

c
or, 1/4 + 1/(x+9) = 1/x x = 3 so, the 2nd hose takes 12 hours check: in 1 hour, the two hoses fill 1/4 + 1/12 = 1/3 of the pool.
September 16, 2014

college algebra
If you mean the increase occurs only for those in excess of 3000, then you have (20)(3000) + (20+0.01)(x-3000) = 153525
September 16, 2014

Coordinate Algebra
In point-slope form, we have y-4 = -3(x-5)
September 16, 2014

Math
what, you don't know how to do any of those steps?
September 16, 2014

Calculus
Well, let's see what they have said. dL = k dT L0 so, L = k*L0*T + C Now you can plug in initial conditions or boundary conditions to determine k and C
September 16, 2014

Math Proof:
Looks to me like you just have to write the definition of inf and sup. a is not in E, but is greater than any other number less than any element of E.
September 16, 2014

physics
Looks like 600N/m^2 assuming it is lying flat on one face
September 16, 2014

math
1 = 1^3 8 = 2^3 27 = 3^3 so, what do you think?
September 16, 2014

Math quadratic word problem
Your very first line is off. For a triangle, A = bh/2
September 16, 2014

Trigo
Draw a diagram. If the pole has height h, and the tip of the shadow is x horizontally away from the pole, then (82 sin8° + h)/x = tan28° x/82 = cos8° Now, eliminate x to get (82 sin8° + h)cot28° = 82 cos8° Now just solve for h
September 16, 2014

math
2/5 + 1/3 = 6/15 + 5/15 = 11/15 That leaves 4/15 as woodwinds. So, 2/15 are clarinets 2/5 * 240 * 1/8 = 12 are tubas
September 16, 2014

Plural of economix?
.
September 16, 2014

math
0.9 x 5.2 / 0.2 x 25 = 585 (0.9 x 5.2) / (0.2 x 25) = 0.936 Pick the one you mean and then subtract 120 to find the missing value.
September 16, 2014

physics
distance = speed * time so, plug and chug
September 16, 2014

math
the only purpose I can see is readability. The math is identical, regardless of representation.
September 16, 2014

Calculus
It is not always possible to find such a tangent line. Consider the graph of y=x^2. No tangent line will pass through the point (0,1), since it lies inside the parabola. However, assuming that the point is properly placed, we need to find a point (x,y) on the graph such that ...
September 16, 2014

Math Problem (please help)
wolframalpha is your friend: http://www.wolframalpha.com/input/?i=6x^4+%E2%88%92+13x^3+%E2%88%92+144x^2+%2B+325x+%E2%88%92+150
September 15, 2014

Calculus-Math
Rolle's Theorem says that since C(2)=C(15), there is some value 2<c<15 such that C'(c) = 0. dC/dx = 12(2x^2-6x-9)/(x(x+3))^2 dC/dx=0 when 2x^2-6x-9=0, or x = 3/2 (1±√3) or, x = -1.1, 4.1 So, your answer of 4 is correct. The graph at http://www....
September 15, 2014

math
since 1/7 does not evenly divide 9/10, the answer is no.
September 15, 2014

math
#1 -14.8 + 22.6 = 7.8 #2 (x - 16) + 5 = -15 x-16+5 = -15 x-11 = -15 x = -4 #3 5 = –(–z + 3) 5 = z-3 8 = z #4 t - 17 = -11 Your choice is the situation where the temperature started at 17° and then decreased by t°.
September 15, 2014

Math
The number is negative, so it is -2.78 Its absolute value is +2.78 So, the distance between the two is 5.56 They are equal distances from 0, but in opposite directions.
September 15, 2014

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

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

Search
Members