Saturday
October 25, 2014

Posts by STEVE


Total # Posts: 26,089

physics
The boat and its contents are floating, so its general density is less than that of water. So, the boat displaces a volume of water which has the same mass as the boat. But a rock is denser, so it displaces less water. SO, the amount of water displaced drops when the rock ...
October 1, 2014

math
d and e are obviously out, since they do not start with 3. Of the others, which has terms that increase by 2?
October 1, 2014

Math
(3*7 + 9*8)/(8*7)
October 1, 2014

math
350P3 = 350*349*348
October 1, 2014

Math
why don't you give it a shot? Just start listing them, but don't list any letter twice.
October 1, 2014

Math
-2(-2)+10 is not 8 use the slope-intercept form: y-8 = -2(x+2) y = -2x + 12
October 1, 2014

Find the pattern
If you start with #8, you can pin down certain days. Surely you can make some headway in this.
October 1, 2014

Pre-caluclus
well, I don't know what "7500 1" means, but I'll just call it 7500 and you can fix it as needed. For the inverse, swap variables and solve for y: t = 7500 + 749e^(-0.15y) t-7500 = 749e^(-0.15y) e^(-0.15y) = (t-7500)/749 -0.15y = log[(t-7500)/749] y = -log[(t-...
September 30, 2014

Math
1 in = 2.54 cm, so you have (2*36 + 2*12 + 5)(2.54) = 256.54 cm Do the other the same way. Next time you get a wrong answer, show your work, and we can fix what's wrong.
September 30, 2014

Math
wow, didn't get far, eh? Just start solving for y: x = (1+2y)/(1+y) x(1+y) = 1+2y x + xy = 1 + 2y x-1 = 2y - xy x-1 = y(2-x) (x-1)/(2-x) = y Easy, no? The domain of f(x) is all real numbers except where the denominator is zero. That is all values except -1. The domain of ...
September 30, 2014

Math
But, just to get you started, if there are $x at 6%, the rest (1000-x) is at 9%. So, add up the interests earned: .06x + .09(10000-x) = 750.00 Now just crank it out.
September 30, 2014

Geometry
the hypothesis comes after "if". so your first answer is correct.
September 30, 2014

Math
13 and 15 occur most frequently. The center value is 15. Depending on how many other numbers there are, just start putting them on both sides of 15 (the median), making sure they always add up to 15*n, where there are n numbers. And make sure that 13 and 15 occur the most.
September 30, 2014

Math z-scores
you can play around with Z stuff at http://davidmlane.com/hyperstat/z_table.html It shouldn't take long to answer your question
September 30, 2014

algebra 2
(ab)^2 - 2^2
September 30, 2014

Precalculus
P(x) = (x-4)(x+5)^2 now it's easy, right?
September 30, 2014

Algebra 1
#1, Clearly not true for x=10 Try C if it's supposed to read 4x^2 <= (4x)^2 because (4x)^2 = 16x^2 #2 A, just as in #1. (5x)^2 = 25x^2 >= 5x^2 take a look at wolframalpha.com, where you can plot several functions on the same axes. For example, http://www.wolframalpha...
September 30, 2014

Trigonometry
The length of the ladder does not matter. We are told that cos x = 1/4 x = 75.52°
September 30, 2014

Math
4(2x + 3) = 2(3x - 4) 8x+12 = 6x-8 2x = -20 x = -10 Bzzzt 6 - a = 1/3(9a - 18) 18-3a = 9a-18 12a = 36 a = 3 correct 3(4x - 3) - 7x = 5x - 9 12x-9-7x = 5x-9 5x-9 = 5x-9 correct - the same line 4(2x - 3) - 4x 8x-12-4x 4x-12 2(2x-6) 4(x-3) only your first choice is correct
September 30, 2014

Trigonometry
You have to know the size of the court. Assuming the spike is driven parallel to the side lines, then if the distance to the far line is x, and assuming you want the angle from the vertical (otherwise you'd be asking for the minimum angle), then x/2.44 = tan θ See how...
September 30, 2014

MATH HELP PLEASE
(5.1 × 10^3) • (3.2 × 10^3) (5.2×3.2)×(10^3×10^3) 16.32×10^6 But that is not scientific notation. The leading number must be at least 1.0, and less than 10, so you need to shift the decimal point and adjust the exponent: 1.632×10^...
September 30, 2014

Trigonometry
surely you know that cos(180°) = -1 so, arccos(-1) = 180°
September 30, 2014

Pre-Calculus/Trigonometry
you could eliminate the x by doing some judicious multiplying: 24x-6y = 15 -24x+6y = 14 Now add the equations to get 0y = 29 BZZZT! No solution
September 30, 2014

math
got me. What is R?
September 30, 2014

College Algebra
since time = speed * distance, then if her outbound speed was x, then 12/x + 12/(x-10) = 1 x = 30 or 4 Check: 12/30 + 12/20 = (24+36)/60 = 1 The other solution to the equation is x=4. Why is that not useful?
September 30, 2014

Math
#1 EVERY function has a domain. A function is a relation between two sets: the domain and the range. The domain of any polynomial function is all real numbers. #2 If you mean f(x) = 1/(x+5), then you are correct (except you meant x ≠ -5) #3 correct If you meant √(x+2)
September 30, 2014

Math
as with any vector of length r on an angle of t, x = r cos(t) y = r sin(t) So, plug in your numbers.
September 30, 2014

math
98 - (-94) = 98+94 = ?
September 29, 2014

Precalculus
use the vertical and horizontal line tests. If no line cuts the graph in more than one place, the function is 1-1 and has an inverse. That is, each x value maps to exactly one y value, and vice-versa.
September 29, 2014

horizon elementry
v = at, so 8 = a(.5) a = 16 m/s^2
September 29, 2014

precal
ok. now what?
September 29, 2014

Precalculus
Look at the bottom row of the table, dude!
September 29, 2014

Material Behavior
I don't know what F is, but dU/dr = Am/r^(m+1) - Bn/r^(n+1) So, plug in r0 and you have dU/dr(r0) = Am/r0^(m+1) - Bn/r0^(n+1)
September 29, 2014

Math
almost. 3/7 = .4286 so -3 3/7 is 2nd in the list
September 29, 2014

Algebra
it means it is ill posed. The math is correct, but the problem doesn't take into account real-world conditions. Just ignore it, as this is an algebra class, not a physics class. Still, you might point it out to the teacher, not that it will do any good.
September 29, 2014

Algebra
well, clearly the temperature is now -247 - 2*11 = -269 The only problem is that hydrogen freezes at -259
September 29, 2014

Math
36+81 = 9(4+9) or 3(12+27)
September 29, 2014

Geometry
If the numbers are m and n, and m is even, then m=2k. If the sum is even, say 2x, then 2k+n = 2x n = 2x-2k = 2(x-k) So, it is clear that n is also even, since it is a multiple of 2.
September 29, 2014

math
2*16 + 2*3 = 38 or, 2(16+5)-4 = 38 why the two ways of writing the expression?
September 29, 2014

Math
recall that (a+b)(a-b) = a^2-b^2 so, (3+√5)(3-√5) = 9-5 = 4 So, to simplify such fractions, look for the "square conjugate" if you will, of the denominator. 4/(3+√5) = 4(3-√5) / (3+√5)(3-√5) = 4(3-√5)/4 = 3-√5 And do ...
September 29, 2014

Algebra
recall that (a-b)(a+b) = a^2-b^2 so, (3+√5)(3-√5) = 9-5 = 4 So, to simplify such fractions, look for the "square conjugate" if you will, of the denominator. 4/(3+√5) = 4(3-√5) / (3+√5)(3-√5) = 4(3-√5)/4 = 3-√5 And do ...
September 29, 2014

Math
4y(2y^4+3y^2+1) 4y(2y^2+1)(y^2+1)
September 29, 2014

math
1+1+3 = 5 1+2+2 = 5 And you can shuffle those around, making 3+3 = 6 ways to spin 5
September 29, 2014

math
well, you have 2.47f+54.1 = 166.21 So, |h-166.21| <= 3.72 166.21-3.72 <= h <= 166.21+3.72 and so on
September 29, 2014

math
f(x-6)+5
September 29, 2014

7th grade math
good work
September 29, 2014

Pre-Calculus/Trigonometry
(3 -1)(2) (5 2)(6) = (0) (22)
September 29, 2014

algebra 2
10 inconsistent 11 consistent dependent 12 consistent independent
September 29, 2014

Pre-Calculus/Trigonometry
no solutions to x+y = 3 x+y = 4
September 29, 2014

Math (Trig)
sin2x+sin4x = 2sin3x cosx cos2x+cos4x = 2cos3x cosx Now divide to get tan3x
September 29, 2014

math
LCM(9,10,14) = 630
September 29, 2014

AP Calc B/C
If u = e^x, then (e^x)/(1-e^2x)^3/2 dx = du/(1-u^2)^3/2 Now you can easily find that the integral is u/√(1-u^2) which is what Reiny provided.
September 29, 2014

Math
If it was T, then T-18-8+1+2+4+5 = 34 T = 48
September 29, 2014

math problem solving
Looks like 5 to me
September 29, 2014

algebra
34m + 14 = 30m + 22 4m = 8 m = 2
September 29, 2014

math
some multiples of 7 and 3 are 21 42 63 84 Looks like they all work
September 29, 2014

DISCRETE MATH
There are 10 letters, with 3 S's, 3 T's, 2 I's, so 10!/(3!3!2!) = 50400
September 29, 2014

engineering science
the direction remains the same, and v can be found by conserving momentum: 10(8) + 6(4) = (10+8)v
September 29, 2014

Quadratic Functions
it means, graph the function, and look where it crosses the x-axis. Those are the solutions to f(x) = 0.
September 29, 2014

Help Please
Of course not. You just need to find x and y such that x^2+y^2 = 361 So, x and y can be 1,√360 2,√357 3,√352 ... √61,√300 √101,√260 and many, many more.
September 29, 2014

SBGG
the perimeter of the wheel is 7π cm = .07π = .022 m So, 132 m/min * 1min/60s * 1rev/.022m = 100 rev/s
September 29, 2014

Calculus
just use the chain rule: let r = log(u) dr/dθ = 1/u du/dθ let u = cos^2(v) du/dθ = 2cosv(-sinv) dv/dθ let v = 4θ dv/dθ = 4 So, dr/dθ = sec^2(4θ) (-2cos4θsin4θ) (4) = -8tan4θ Or, you could just recall that log(cos^2(4θ...
September 29, 2014

math mks
I see it as what was the temperature at 9 am? -8+15 = 7
September 29, 2014

math
in theory, the ball will never come to rest, since its bounce height is never zero. But, you can see the height of the nth bounce is 7(2/3)^n So, since the distance traveled is both up and down, the sequence is 7 + 2*7(2/3) + 2*7(2/3)^2 + ... so, if r=2/3, = 7 + 14(r+r^2+...) ...
September 29, 2014

Math
a^x is an exponential function, for any number a. the quotient (hence the ratio) of two polynomials is called a rational function.
September 28, 2014

Finite
sounds like real life.
September 28, 2014

math
the fraction riding bikes is 5/32, so of the 800 5/32 * 800 rode bikes.
September 28, 2014

Find the pattern problem solving
taxi: 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 ... bike/trike: 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 moped: 9 15 21 27 33 39 45 51 57 truck: 1 25 35 55 49 30 taxis 9 mopeds 5 trucks so, 16 humans: 12 bikes, 4 trikes total wheels: 4*30 + 9*2 + 5*6 + 12*2 + 4*3 = 204
September 28, 2014

MATH
horizontal has slope 0, so y does not change. So, the line is y=8
September 28, 2014

algebra
If she spends x hours cycling, the rest (8.5-x) is spent running. Since distance = time * speed, 14x + 8(8.5-x) = 101 Now just solve for x and figure 8.5-x
September 28, 2014

math
28 - 9x = -12 - 11x as you say, add 9x to both sides, and you get 28 = -12 - 2x Now add 12 to both sides and you get 40 = -2x Now divide by -2 and you get -20 = x There's no reason to add 11x to both sides after all the x's are together. If you did do that, you have 28...
September 28, 2014

statistics
If the distribution is normal, and the std is high enough, the probability could approach 0.5
September 28, 2014

Algebra
just use the good old distributive property: (2nr - nr^2)r - (2nr - nr^2) . 2r 2nr^2 - nr^3 - (2nr^2 - 2nr^3) 2nr^2 - nr^3 - 2nr^2 + 2nr^3 nr^3
September 28, 2014

math.help pls
f(x)=(472 - 2x^2)^1/3 so, f(8) = (472 - 128)^1/3 = 344^1/3 f(8+h) = (472 - 2(8+h)^2)^1/3 = (344 - (32h+2h^2))^1/3 By the binomial theorem, that is 344^1/3 - (1/3)(344^-2/3)(32h+2h^2) + a bunch of stuff with higher powers of h Now subtract and you have f((8+h)-f(8)) = (-1/3)(...
September 28, 2014

Math
that is correct
September 28, 2014

Calculus
Reiny's solution is cool, using implicit differentiation. You can also do it by noting that 2 = e^(ln 2) So, 2^x = e^(ln 2 * x) and now use the chain rule: d/dx e^u = e^u du/dx, so d/dx e^(ln 2 * x) = ln2 * e^(ln 2 * x) = ln2 * 2^x
September 28, 2014

AP Calc. AB
clearly, due to conservation of energy, etc., the arrow will strike with the same velocity as it left, but in the opposite direction. just solve 53t - 0.62 t^2 = 0 t(53-0.62t) = 0 t = 53/0.62 = 85.4839
September 28, 2014

Math
I think you meant 12a^2 - 5a - 2 = (3a-2)(4a+1) After the path, each dimension is increased by 2, so the new total area is (3a-2+2)(4a+1+2) = (3a)(4a+3) Now subtract the original area to get the area of the path: (3a)(4a+3)-(3a-2)(4a+1) now just simplify that Finally, just ...
September 28, 2014

Math
since C = 2πr, and speed = distance/time, speed = 2π*15000 mi/18 hr = 5236 mi/hr
September 28, 2014

Math
only if the angles are right angles so that the diagonal satisfies the Pythagorean Theorem. That is, if 80^2 + 32^2 = 86^2 does it?
September 28, 2014

Pre-Calc (Point of Inter.)
This problem is discussed at https://answers.yahoo.com/question/index?qid=20101127042533AA17HTY
September 28, 2014

Algebra 2
For x tables and y chairs, we want to maximize p=100x+80y subject to 3x+2y <= 42 2x+6y <= 42 Now use your favorite linear programming tool to find that they make the most with 12 tables and 3 chairs.
September 28, 2014

Pre-Calc (Circles). Please help :(
the area of C5 = 25π The area of the annulus between C3 and C4 is 16π-9π = 7π so, p = 7/25
September 28, 2014

math analysis
we want 1/x < ε 1/ε < x So, if x > 1/ε, 1/x < ε
September 28, 2014

High school algebra
it is well known (and should be noted by you) that 60 mi/hr = 88ft/s So, you have (88/60)(88) = 129 1/15 ft/s
September 28, 2014

Geometry
the midpoint is just the average of the two ends, so its coordinates are x = (-4+9)/2 = 5/2 y = (-2-6)/2 = -4 So, M = (5/2,-4) It would be better had you posted your work, so we could verify accuracy or note mistakes. Also, answer keys are sometimes wrong, so that's always...
September 28, 2014

maths
assuming a constant rate of cooling, it will take x total minutes, where 300 - (300-200)/3 x = 70 x = 6.9 So, in 3.9 more minutes it will have cooled to 70°F
September 28, 2014

geometry
The two radii are r and 14-r, so πr^2 + π(14-r)^2 = 160π (assuming the strange character is supposed to be pi) r^2 + 196 - 28r + r^2 = 160 Now just solve for r.
September 28, 2014

Calculus Minima Problems
if she lands a distance x from the closest point on shore, she is 6-x from the village. So, she will row √(x^2+36) km run 6-x km So, her travel time will be t = √(x^2+36)/10 + (6-x)/20 dt/dx = (2x - √(x^2+36)) / 20√(x^2+36) Since the denominator is ...
September 28, 2014

math
since the figure is isosceles, the diagonals are equal. So, 8x-7 = 5x+2 Now, just solve for x and evaluate the length.
September 28, 2014

trigo
Ah. If you just wanted to verify that cos 3x = 4cos^3 x - 3cos x, then consider cos 3x = cos(2x+x) = cos(2x)cos(x) - sin(2x)sin(x) = (2cos^2(x)-1)(cos x) - (2sin x cos x)(sin x) = 2cos^3(x)-cos(x) - 2sin^2(x)cos(x) = 2cos^3(x) - cos(x) - 2(1-cos^2(x))cos(x) = 2cos^3x - cosx - ...
September 28, 2014

trigo
If you want to know the solutions to 4cos^3x - 3 cos x = 0, cos x (4cos^2 x - 3) = 0 so, cos x = 0 or cos x = ±√3/2 You should recognize those values, as they come up often.
September 28, 2014

algebra
Been there, done that, half an hour ago. It helps if you check your previous posting before doing it again... http://www.jiskha.com/display.cgi?id=1411871416
September 27, 2014

math
A square is the largest area for a given perimeter, if all sides are included. In this case, one side is not, so suppose the side parallel to the wall has length x, and the other sides have length y. x+2y = 24 The area is a = xy = (24-2y)y = 24y-2y^2 You know that this is just...
September 27, 2014

geometric sequence
ar + ar^4 = 7/2 ar^2 + ar^5 = -7 divide and you have r(1+r^3) / r^2(1+r^3) = -1/2 1/r = -1/2 r = -2 So, a = 1/4 Check. The sequence is 1/4 -1/2 1 -2 4 -8 -1/2 + 4 = 7/2 1 + (-8) = -7
September 27, 2014

algebra
Work with the total cost of each part of the mix. They have to add up the the final cost. So, if there are x lbs of $8 coffee, the rest (60-x) has to be the $4 coffee. 8x + 4(60-x) = 5.25(60) x = 18.75
September 27, 2014

Algebra 1
just collect terms with the same power and then simplify: 6-t-t^4 + 9t+t^4 = (-1+1)t^4 + (-1+9)t + 6 = 8t+6 It is customary to list the highest power first, and then descend. Notice how the t^4 terms vanish because -1+1 = 0
September 27, 2014

algebra
well, just plug in your numbers: f(35) = 0.019*35^2 + 35 + 14 = 72.275 and so on with other values
September 27, 2014

Algebra
Since the fence is mentioned, you really should check to see that the ladder will clear the fence. Using the given distances, and similar triangles, if the ladder lies on top of the fence, it will reach up to a height h, found by 9/8 = h/10 h = 12.5 In this case, the ladder ...
September 27, 2014

physics
5π/4 what about it? It's just a number. It is much easier to use in calculations than its decimal approximation of 3.927
September 27, 2014

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