Friday
October 31, 2014

Posts by steve


Total # Posts: 26,264

Algebra - typo?
You know, we work hard to provide help with the problems. Don't make us read your mind as well. And shoot, why not show some of your own work to help us figure out what is troubling you? If you mean to find the solution to the system of equations -7x+8y=-8 -2x+6y=-6 If you...
September 9, 2014

math
they are approaching at the rate of 18 mi/hr They only had to cover 5 miles, so that took 5/18 hours In that time, Jim ran 10 * 5/18 = 25/9 miles
September 9, 2014

Pre-Calculus/Trigonometry
A is true because the 2nd entry for x is 5, and the 2nd entry for f(x) = 6 Now for the others, the domain is the set of x values. The range is the set of f(x) values. D is just like A. That should help some.
September 9, 2014

Pre-Calculus/Trigonometry
there's nothing to solve. Just evaluate the expression. I tend to think that you meant 3/(x+2) - √(x+3) but it's hard to say due to your carelessness with parentheses. If I got it right, then it just evaluates to 3/(7+2)-√(7-3) = 3/9 - √4 = 1/3 + 2 = ...
September 9, 2014

Pre-Calculus/Trigonometry
well, I'd say that it's 3/7+2-√7-3 Insert parentheses as need for proper evaluation!
September 9, 2014

Physics
the velocity changed by -44 m/s in 4.8s, so the acceleration is -44/4.8 m/s^2
September 9, 2014

Math
the minimum cost is found at the vertex of the parabola. As you recall, that is at x = -b/2a, or in this case x = 10/.5 = 20
September 9, 2014

maths
cos(t) = 1.5/3 = 1/2 t = π/3 or 60° Better review you standard 30-60-90 and 45-45-90 triangles. They pop up often.
September 9, 2014

math- help needed badly
The ship travels 20 miles in the time given. If we label the points S for ship (current position), N and F for Near and Far lighthouses, then if we call the original position O, In triangle SNF, S=25° N=125° F=30° In triangle ONS, n = 20 N=55° O=95° so, NS/...
September 9, 2014

Calculus
You have x,y r^2 = x^2+y^2, so r = √29 Now just plug and chug: sin = y/r cos = x/r tan = y/x and so on
September 8, 2014

Precalculus
75/x = tan 40° I assume you meant 40°, not 40', as that would have (a) been hard to measure (b) put the ship well over the horizon
September 8, 2014

math
Nope. C time to review
September 8, 2014

AP CAlc. AB Please helppp!!
As usual draw the graph. Clearly for r < 0, f(x) = -x + 1, so A(r) = ∫[-2,r] -x+1 dx For r > 0, we have f(x) as -x + 1 for -2 <= x <= 0 x + 1 for 0 < x <= r So, A(x) = ∫[-2,0] -x+1 dx + ∫[0,r] x+1 dx Both of those are easy to evaluate, so ...
September 8, 2014

algebra
width: w length: 2w+5 so, 2(w + 2w+5) = 46 Now you can get w, and then 2w+5.
September 8, 2014

Pre-Calculus/Trigonometry
Uh, look at the table. 1 is the 5th entry in the x row 1.3 is the 5th entry in the f(x) row. So, f(1) = 1.3
September 8, 2014

Math Proof
sure could. But the argument is the same. Might as well work with what you were given, in this case at least.
September 8, 2014

Math Proof
Looks good. This is the method usually used to prove that √2 is irrational, but it works for any integer. You can find lots of proofs for that online. Look some up, and see how they use the same argument.
September 8, 2014

Math
clearly, the deduction will be .062*3260 + .0145*3260 It will be the same for all her paychecks, since her annual earnings will fall well short of the SS cutoff point.
September 8, 2014

MATH HELP
Now: 46 At the end of Day 1: 38 Day 2: 30 Day 3: 22 Day 4: 14 - order more Day 5: 6 Day 6: out of stock unless more has arrived
September 8, 2014

Math Proof
sum: Assume that it is rational. That is, if c = a/b, then a/b + x = m/n for some integers m and n. That means that x = m/n - a/b But m/n-a/b = (bm-an)/(bn), clearly a rational number, and x is irrational. So, if x is irrational, c+x cannot be rational. Clearly, cx must also ...
September 8, 2014

math
Assuming you mean (6x)^2 = (6x)(6x) = 36x^2 or, (6x)^2 = 6^2 * x^2 = 36x^2
September 8, 2014

math
D additive identity = 0 multiplicative identity = 1 a+0 = a a*1 = a for any value of a
September 8, 2014

math
hint. substitute to get 6x + 4(3-3x) = 0
September 8, 2014

math
1/2
September 8, 2014

math
since there are three values of x which satisfy the equation, there are three values for 2x+3.
September 8, 2014

math
(3,4/3)
September 8, 2014

math 1 question
powers first: 25-4/5+2 then multiplication and division, left to right: 25 - 0.8 + 2 then addition and subtraction, left to right: 24.2+2 26.2
September 8, 2014

Math
You have 26*1760+385 = 46145 yards since 1 meter = 1.0936 yards, that means you have 46145/1.0936 = 42195 meters When you get stuck, it's best to post your work -- that way we can help figure out where you went wrong. Just sayin'
September 8, 2014

algerbra
divide the second by 3 and you will see that they are the same line.
September 8, 2014

phycis
since mass * distance is the same, and the heaver mass only rises 1/6 as far, it is 6 times the mass, or 360N
September 8, 2014

Math
what is 1000000/100? It's 10,000 So, 10,000 CDs to each of 100 stores makes 1,000,000. 925,733 The 2nd 3 is just 3 The others are true
September 8, 2014

math
Hmmm. If the sides are in the ratio 4:5:6, then the sines of the angles are in the same ratio (law of sines) So, if sinA = 4x, sinB = 5x sinC = 6x arcsin(4x)+arcsin(5x)+arcsin(6x) = pi x = √7/16 A = arcsin(4√7/16) = 41.41 B = arcsin(5√7/16) = 55.77 C = arcsin...
September 8, 2014

Math
Id say f(x) = x h(x) = 4 f(x)
September 8, 2014

math
since the slope is the same, they are either parallel or the same line. I expect you can decide which. If parallel, no solutions, since they do not intersect. If the same line, there are infinitely many solutions, since any point on one line is also on the other.
September 8, 2014

algerbra
well, did you try any to see whether they are? (0,-1): -1 = 6*0-1? yes and so with the others.
September 8, 2014

calculus
∂u/∂x = 2x/(x^2-y^2) ∂u/∂y = -2y/(x^2-y^2) ∂2u/∂x∂y = ∂2u/∂y∂x = -2(x^2+y^2)/(x^2-y^2)^2
September 8, 2014

math check answers
I like all your answers. On #2, the markup based on cost is indeed 67%. The markup based on salling price is 40%, since the $100 markup is 40% of the $250 selling price. Could be they had a typo in the question or mixed up the answers.
September 8, 2014

Math
24(1.06)^(2013-1626) = $1.49*10^11 you may adjust it depending on whether the final year was an entire year.
September 8, 2014

math - eh?
sounds like a good deal. Is there a question in there somewhere?
September 8, 2014

Algebra
width: w length: w+11 so, 2(w + w+11) = 90 Now just solve for w, and figure the length.
September 7, 2014

Algebra
How approximate? Assuming you meant f(x) = -8x^2 + 2x + 2, f(-1) = -10 f(0) = 2 f(1) = -6 So, f(x)=0 somewhere in (-1,0) and (0,1). You can, of course, use the quadratic formula to get an exact answer and then approximate with as many decimal places as you wish. See http://www...
September 7, 2014

math - eh?
Heck, I can't even figure out what the string of digits and slashes even means! Maybe some parentheses around the terms will help. And two = signs? What's up with that?
September 7, 2014

math
If there are x lbs of 4.40 tea, then the rest (120-x) is 2.30 So, we need 4.40x + 2.30(120-x) = 3.00(120) Now just solve for x.
September 7, 2014

Math
If P(x) = x^2-4x, then since P(x) = x(x-4), it has two x-intercepts. Q(x) = x(x^2-4) = x(x-2)(x+2) so Q has 3 roots. x^2-ax = x(x^2-a) = x(x-√a)(x+√a) so there are 3 roots With 3 roots, there must be 2 extrema. x^2+ax = x(x^2+a) since a>0, x^2+a can never be ...
September 7, 2014

Calculus
x + y − 1 = ln(x^5 + y^5) 1 + y' = 1/(x^5+y^5) (5x^4 + 5y^4 y') y'(1 - 5y^4/(x^5+y^5) = 5x^4/(x^5+y^5) - 1 y' = ((x-5)x^4 - y^5)/(x^5 + (y-5)y^4) At (1,0), y' = (-4)/(-1) = 4 So, the line is y = 4(x-1)
September 7, 2014

math
18s^9 t^3 - 2s^9 t^2 can be factored into 2s^9 t^2 (9t-1) No idea how that can be evaluated to 9. I suspect there is something missing or garbled in the problem statement as shown.
September 7, 2014

math
341-115 = 226 341-120 = 221 So, any value between 221 and 226 will produce a number between 115 and 120. Or, using a compound inequality, we have 115 < 341-x < 120 -226 < -x < -221 226 > x > 221
September 7, 2014

math
You can figure out the mass of silver, then do all the conversions of mass to volume and back, or you can note that density(Al)/density(Ag) = 2.57 So, volume(Al)/volume(Ag) = 2.57 But, the volume of a sphere scales as the cube of the radius, so the radius scales as the cube ...
September 7, 2014

math
(12-2)p^7 = 10p^7
September 7, 2014

algebra
do it just the way to multiply 2-digit numbers: (23)(45) = (20+3)(40+5) = 20*40+3*40+10*5+3*5 = 1035 (7-6y)(7-4y) = 7*7 + 7(-4y) - 6y(7) - 6y(-4y) = 49 - 28y - 42y + 24y^2 = 49 - 70y + 24y^2
September 7, 2014

algebra 2
all polynomials have domain of all real numbers. All polynomials of odd degree have range of all real numbers, y=0 when x = ∛4 x=0 when y = -4
September 7, 2014

Calculus
You know the roots are x = (m±√(m^2-4))/2 So, if m<=2 there are not two real roots, so the total area is the same as the integral. If m>2, then you need to divide the integral into 3 parts, with the roots as the limits of integration. Reiny's solution of...
September 7, 2014

Algebra
You have two points on the line: (2,5) and (6,9). So, the line has slope=1, and its equation is c = m-3
September 7, 2014

Geography
∂2u/∂x∂y
September 7, 2014

physics
8.2m / 3.7m/s = 2.2 s
September 7, 2014

physics
just solve for a in 4100t - 17/2 t^2 = 9400t - a/2 t^2 a/2 t^2 = 5300t + 17/2 t^2 at^2 = 10600t + 17t^2 a = 10600/t + 17
September 7, 2014

Quick question
Just how would you propose we do asl in a text forum?
September 7, 2014

Calculus
clearly, each rectangle with upper-right corner at (x,y) has area a = xy Since y = 9-x^2, the area is just a = x(9-x^2) Not sure what you need to do with that information. The question is a bit vague.
September 7, 2014

Math - Urgent
(a) each term is -1/3 the previous term (b) each term is -4 times the previous term Just take the first two terms and find their ratio. Then check to make sure the same ratio is there for the next two terms, and so on.
September 7, 2014

math
the slope of the given line is -1/2 so, the slope of perpendiculars is +2 So, the line you want is y+12 = 2(x+7)
September 7, 2014

Precalc
try C(x) = 4.00 + 0.40⌈10x⌉ where ⌈z⌉ is the ceiling function (the least integer greater than z) For example, ⌈2.37⌉ = 3
September 7, 2014

science/math (mean)
I get 44.60333333... So, to three decimal places, that would be 44.603 However, since all the values are given to two places, I would have given the same answer you did.
September 7, 2014

math
6*22 + .18 * 2766.50 = 629.97
September 7, 2014

math 8
when multiplying powers, add the exponents. when raising a power to a power, multiply exponents. This is because, for example, (x^2)^3 = (x^2)(x^2)(x^2) = x^(2+2+2) So, you have #5: 8^3 * 8^7 = 8^(3+7) = 8^10 #11: (5/8)^3 = 5^3/8^3 = 125/512 #12: ((-2/9)^3)^5 = (-2/9)^15 = -2^...
September 7, 2014

C programming
Hmm. Looks good to me. Can you produce the results for a few values of x? Do you at least get cosh(0) = 1.0 ?
September 7, 2014

math 12
If C=D, C-D=0 and you cannot divide by zero.
September 7, 2014

Math
graphing what?
September 7, 2014

physics
658.1m / .03m/yr = 21936.7 yr
September 7, 2014

physics
in MKS units, .440kg * 98 mi/hr * 1000m/0.62mi * 1hr/3600s = .440*98*1000 / .62*3600 m/s = 19.32 kg-m/s
September 7, 2014

Algebra
correct. So, plug in either point. Using (-2,-3), you have -3 = (-2/7)(-2) + b b = -25/7 so, y = -2/7 x - 25/7
September 7, 2014

Physics
x(3) = 90m x(2) = 40m total distance: 50m total time: 1s avg speed: 50 m/s
September 7, 2014

Math
going down: 5/2 seconds going up: 5/1 seconds so, down+up = ?
September 7, 2014

Geometry help
Did you draw a diagram? AC = CD AD = AC+CD #1 ok #2. The calculation for x is just as in #1. AD = AC+CD = 7+7 = 14 #3. AD=AC+CD = 2(AC), so 6x-4 = 2(4x-3) x = 1 CD = 1 #4. As in #3, 12-x = 2(3x-1) x = 2 CD = 5
September 7, 2014

AP Alegebra
(√x+1)/(√x-1) multiply top and bottom by √x+1 and you have (√x+1)(√x+1) / (√x-1)(√x+1) (x+2√x+1) / (x-1)
September 7, 2014

Law of Sines
you have C and c and a, so you can find A using sinA/a = sinC/c Now, having A and C, you know that A+B+C=180, so you can easily find B. Then, use the law of sines again to get b: b/sinB = c/sinC = a/sinA
September 6, 2014

Algebra
reflecting through where? x-axis? y-axis? origin? Just to remind you, reflecting through x-axis: (x,y) -> (x,-y) y-axis: (x,y) -> (-x,y) (0,0): (x,y) -> (-x,-y)
September 6, 2014

AP CAlc. AB
since |sinx| <= 1, x^2 sin(1/x) -> 0 as x->0 So, all that's left is 3k. Doesn't really matter whether k is positive or not.
September 6, 2014

Physics II
What is the sign and magnitude of a point charge that produces a potential of -2.00 V at a distance of 3.00 mm?
September 6, 2014

Calculus
As a sequence, let Tn be the time taken to meet the car for the nth time. T1 = d/(b(c+1)) T2 = T1*b/(b(c+1)) ... Tn = d/(b(c+1))^n The sum of this series, with a = d/(b(c+1)) r = 1/((c+1)) is S = a/(1-r) = d/(b(c+1)) / (1 - 1/((c+1)) = d/bc That is the total flying time. So, ...
September 6, 2014

AP Physics
since time = distance/speed, 16.5/s + 16.5/340 = 2.90 s = 5.787 m/s
September 5, 2014

AP Physics
since the car is going 17 km/hr faster, and it is 0.130 km behind the truck, it will take 0.130/17 = 0.0076 hours You may want to express that in seconds :-)
September 5, 2014

math
that would be 21*16 + 18*20 = 696g
September 5, 2014

math
P = a-c = (a+b)-(b+c) = 49-13 = 36
September 5, 2014

algebra
y increases by 4 when x increases by 1. So, look for something like y = 4x+b Now, when x=1, y=0, so we end up with y = 4x-4
September 5, 2014

algebra
the height is the y-value at the vertex, where x = .658/.000814 Since y = x(.658-.000407x) the roots are at 0 and 1616.7 The bridge spans that distance
September 5, 2014

algebra
first rearrange the terms so you have 2x^2 + 2x - 5 = 0 Now just plug in the formula, where a = 2 b = 2 c = -5 x = (-2±√(2^2 + 4*2*5))/(2*2) = (-2±√44)/4 = (-1±√11)/2
September 5, 2014

math
using the same ratio, x/125 = 400/20000 x = 2.5
September 5, 2014

Physics
(a) 31.1t = 1/2*4.11t^2 t = 15.134 seconds Now use that t for parts (b) and (c)
September 5, 2014

Physics
see related questions below, and change the numbers as necessary. The key is to separate the 2.2 seconds into the falling time and the return time.
September 5, 2014

math
review scientific notation. There is a number and a power of 10. the number must be between 1 and 10. (Less than 10) When adding, the powers of 10 must be the same, just as you need a common denominator to add fractions. Then you can just add the numbers as usual, keeping the ...
September 5, 2014

Math
the chance it will not snow on a day is 3/5, so for two days, that is 3/5 * 3/5 = 9/25
September 5, 2014

Math
the ratio of 3.25in : 4cm for the short side is 3.25*2.54/4 = 2.07 close enough for jazz. Now use that scale factor to enlarge 4.6cm. Probably should express the answer in inches, as well, since that was the original frame size unit. Actually, you don't need the scale ...
September 5, 2014

math
just drag out your formula for the area of a circle: A = πr^2 In this case, r = 7 yd, so A = π(7 yd)^2 = 49π yd^2
September 5, 2014

Operating Systems
pages are accessed in the order acbd*a*c*b*d*e*f* Bad luck, that.
September 4, 2014

math
each photo is 2x2, so 2*60 = 120
September 4, 2014

Math
you can solve for x or for y. Which is of interest to you?
September 4, 2014

math word problem
300(1+.04)^5
September 4, 2014

Pre-Calc
As usual, draw a diagram. It is clear that if the height of the mountain is h, and the tower is at a distance x from the mountain, (h-180)/x = tan 21°35' h/x = tan 24°48' Eliminate x and you have (h-180)/tan21°35' = h/tan24°48' Now just solve for h
September 4, 2014

Geometry
I'd say 56 and 75 Maybe a bit more context would be helpful...
September 4, 2014

AP Physics
total distance: 7.7*4.5*60 + 2.8*2.8*60 = 2549.4 m total time: (4.5+2.8)*60 = 438 s so, avg velocity is 2549.4/438 = 5.8 m/s
September 4, 2014

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