Sunday
November 23, 2014

Posts by steve


Total # Posts: 26,936

Algebra
slope = -3/2 use the point-slope form, then change to slope-intercept: y-7 = -3/2 (x-5) y = -3/2 x + 29/2 The line is vertical, since both points have the same x-coordinate. So, x = -5 Always check for horizontal/vertical lines first.
October 30, 2014

Math help!
√((4+2)^2+(-6-2)^2) = √(6^2+8^2) = √(36+64) = √100 = 10 Better check your + and - signs
October 30, 2014

Math
f(t) = 15(t-3)(t-10) Clearly f(t) < 0 on the interval (3,10)
October 30, 2014

math
f(x) increasing when f'(x) > 0 f'(x) = 4x^3 - 60x^2 + 282x - 414 = 2(x-3)(2x^2-24x+69) The roots are 3,6±√(3/2) = 3.00,4.78,7.22 So, f' > 0 in (3,6-√(3/2) U (6+√(3/2),∞)
October 30, 2014

Pre calc
500 x 1000 area = x(2000-2x)
October 30, 2014

Trigonometry
multiply by 1-tanx to get (1-tanx)^2/(1-tan^2 x) = (1-2tanx+tan^2 x)/(1-tan^2 x) = (1+tan^2 x)/(1-tan^2 x) - 2tanx/(1-tan^2 x) = sec^2x/(1-tan^2 x) - tan2x = 1/(cos^2x-sin^2x) - tan2x = 1/cos2x - sin2x/cos2x = (1-sin2x)/cos2x Your carelessness with parentheses threw me off for...
October 30, 2014

Calculus
see the related questions below; just change the numbers.
October 30, 2014

algebra
x + 2/3 x + 1/2 x + 1/7 x = 97 97/42 x = 97 x = 42 check: 42 + 28 + 21 + 6 = 97
October 30, 2014

business math
c/4 - 6
October 30, 2014

statistics
4% lie 1.75 std below the mean. So, 60000-5000*1.75 = 51250 If the warranty is for 51250, 96% of the tires will exceed that mileage. You can enter your values and play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
October 30, 2014

Math
Draw your Venn diagram of three intersecting circles. 30 in the center part Since 55 are married and have a cell phone, that leaves 25 in the unlabeled intersection of married and cell. Similarly, 5 in the cell-car intersection not already labeled. 25 in the unlabeled part of ...
October 30, 2014

Algebra
correct
October 29, 2014

Algebra 2
as with all parabolas, the vertex is at x = -b/2a, in this case t = 3 So, plug that in to get the max height f(t) = 16t(6-t) That will tell you how long it takes to hit the ground (f=0) As usual, the vertex is midway between the roots.
October 29, 2014

math
d = (135-100)/5 = 7 100+7 = 107
October 29, 2014

AP physics
we have initial velocity (Vx,Vy) y = Vy t - 4.9t^2 4.8Vy - 4.9*4.8^2 = 0 Vy = 23.52 x = Vx t 52 = Vx * 4.8 Vx = 10.83 So, v^2 = 10.83^2 + 23.52^2 v = 25.90 at an angle θ such that tanθ = Vy/Vx = 23.52/10.83 = 2.17 θ = 65.28° Now you can plug those values ...
October 29, 2014

Math
what, no calculator? Much faster than posting it here and waiting for a response.
October 29, 2014

Math
it's not an equation. It's just an expression. Punch in the numbers on your calculator to see its value.
October 29, 2014

math
leap years have 366 days
October 29, 2014

math
x = (c-7000)/210 No calculus needed; just algebra I
October 29, 2014

math
11/24 - 3/8 = 11/24 - 9/24 = 2/24 = 1/12
October 29, 2014

math
(2/3)(1/3)x = 4 2/9 x = 4 x = 18 check: spent 12 at A leaving 6 spent 2 at B, leaving 4
October 29, 2014

calc
v = 4/3 pi r^3 dv/dt = 4pi r^2 dr/dt a = 4pi r^2 da/dt = 8pi r dr/dt = 8pi r (dv/dt / (4pi r^2)) Now just plug in dv/dt and r
October 29, 2014

calc
PV^1.4 = C using the product and chain rules, V^1.4 dP/dt + 1.4PV^.4 dV/dt = 0 now just plug in your numbers
October 29, 2014

calc
After t hours, A is at (-(30+17t),0) B is at (0,16t) So the distance d is found by d^2 = (30+17t)^2 + (16t)^2 = 545t^2 + 1020t + 900 at t=6, d = 163.22 So, now we can find the rate of change for d: 2d dd/dt = 1090t + 1020 2*163.22 dd/dt = 7560 dd/dt = 23.16 knots
October 29, 2014

Algebra I
Short answer: yes, you are correct. Some explanation... just watch the units. You can always multiply by 1 without changing the value of the expression. 1m = 100cm, so 1m/100cm = 1 100cm/1m = 1 Now, keep the units with the values. They cancel, just like factors: 42m * 100cm/1m...
October 29, 2014

currency exchange/ math
U$130 * C$!/U$0.9315 = C$139.56 the commission is C$139.56 * 0.0055 = 0.77 So, the final amount received was 139.56-.77 = 138.79
October 29, 2014

math
1.8*0.3 = 0.54 each multiplicand has one decimal place. So, the product has two. Also, just by observation, 1.8 is almost 2, so the answer should be about twice as big as 0.3 (0.6)
October 29, 2014

math
fix the garbled sentence eye was three times as old .
October 29, 2014

math
since time = distance/speed, (d/2)/5 + (d/2)/10 = 3 d = 20 check: 10/5 + 10/10 = 2+1 = 3 hrs
October 29, 2014

Math
n! is basically an nth-degree polynomial (2n)! is a 2n-th degree polynomial n^n is an nth-degree polynomial so, (2n)!/n^n -> n^2n/n^n is like an nth-degree polynomial, and -> infinity
October 29, 2014

algebra
see all the details here: http://www.gregthatcher.com/Mathematics/GaussJordan.aspx Just enter your coefficients and watch the fun
October 29, 2014

Geometry
well, just do what the rule says: (x,y)->(x,y-5) = (-8,-3) means x = -8 and y-5 = -3 x = -8 and y = 2 reflection: (x,y)->(-5-(x+5),y) = (-x-10,y) glide: (x,y)->(x,y-5) means (-x-10,y) -> (-x-10,y-5) So, P->(-8,-3) = (-x-10,y-5) means that -x-10 = -8 y-5 = -3 x...
October 29, 2014

geometric progression
T6 = ar^5 = a*10^5 = 2000 a = 2*10^3 / 10^5 = 2*20^-2 = 0.02 Check: 0.02 0.2 2 20 200 2000 ...
October 29, 2014

calculus
LOVE IT! Assuming the lantern is in fact shining, we have If the length of rope from the man to the pulley is z, and the man is x ft away from the wall, we have x^2+30^2 = z^2 z dz/dt = x dx/dt when x=40, z=50 and the lantern is at height 36-10 = 26 If the lantern is at height...
October 29, 2014

geometry
I pick D
October 29, 2014

math
150/x = tan 34°
October 29, 2014

Algebra
That's because there's a mistake in the problem. Even if it were all invested at 4.2%, she'd earn .042*15000 = $630 in interest. That $21 interest is bogus. It must be $2100 or something.
October 28, 2014

AP Calculus
infinite discontinuities are not removable. (x^2+4x+3) = (x+3)(x+1) x^2-9 = (x+3)(x-3) So, for all values of x except x = -3, f(x) = (x+1)/(x-3) At x = -3, f(x) = 0/0, which can be any value; it is undefined. The discontinuity there is removable, if f(-3) is defined to be 1/3.
October 28, 2014

Calculus
2x + y + xy' + 2yy' = 0 y'(x+2y) = -(2x+y) y' = -(2x+y)/(x+2y) So, y'=0 when 2x+y = 0 So, if y = -2x, x^2-2x^2+4x^2 = 6 3x^2 = 6 x = √2 So, y = -2√2 At (√2,-2√2) and (-√2,2√2) the tangent is horizontal. Check: http://www....
October 28, 2014

Geometry/Algebra
y-7 = -5/2 (x+4) y-7 = -5/2 x - 5/2(4) y-7 = -5/2 x - 10 y = -5/2 x - 3
October 28, 2014

Math
f'(x) = x(2logx - 1)/(logx)^2 So, since f and f' are not defined at x=0, f'(x) = 0 when 2logx = 1 logx = 1/2 x = √e f(√e) = e/(1/2) = 2e See the graph at http://www.wolframalpha.com/input/?i=%28x^2%29%2F%28ln%28x%29%29+for+x+%3D+0..3
October 28, 2014

Math
well, you need 1/3 pi(5^2)h = pi(5^2)(12) 1/3 h = 12 h = 36 This should be clear since the volume of a cone is 1/3 the volume of an equivalent cylinder. So, if you want the cone of the same radius to have the volume of a cylinder, it must be 3 times as tall.
October 28, 2014

Calculus
as usual for quadratics, the vertex is at t = -b/2a = 308/(14/3) = 66 Odd, since g is 1/6 of earth's, I expected the equation to be -16/6 t^2
October 28, 2014

Calculus
wh = 380 a = (w+16)(h+4) = (w+16)(380/w + 4) = 4w + 444 + 6080/w da/dw = 4 - 6080/w^2 minimum area when da/dw = 0. So solve that and evaluate w and h. Then the poster dimensions are w+16 and h+4.
October 28, 2014

Calculus
set da/dw = 0 when w + 2h + πw/2 = 49 a = wh + π/8 w^2 = w(49 - (1+π/2)w)/2 + π/8 w^2
October 28, 2014

Calculus
If the base has width 2x and height y, then the area is a = 2xy = 2x(4-x^2) so find x when da/dx =0
October 28, 2014

Algebra 2 & trig
If x at 5.5%, the rest (7500-x) is at 6%. So, add up the interest: .055x + .06(7500x) = 435
October 28, 2014

Math 130
The lateral area is just 2πrh, so doubling either has the same effect The area of the ends, however, is 2πr^2, so it's likely that doubling r has a greater effect. However, since the area is not directly proportional to either, the relative sizes of r and h will ...
October 28, 2014

calculus
inflection points where f" = 0 f" = 2(2-9x^2)/(3x+2)^2 f"=0 when 2-9x^2 = 0
October 28, 2014

Math
you have approximately 300mi/10hr or about 30 mi/hr Clearly (4) is the only viable choice
October 28, 2014

algebra 2
plug in x=1 and y=2 (1+2)^-2 = 1/9 1^-2 + 2^-2 = 5/4
October 28, 2014

Physics
to conserve momentum, (1.93*10^4)(3.12) + (2)(1.93*10^4)(1.04) = 3(1.93*10^4)(v) 3.12+2.08 = 5.79v v = 0.898 m/s Old KE = 1/2 m*3.12^2 + 1/2 * 2m * 1.04^2 = 5.949m new KE = 1/2 * 3m * 0.898^2 = 1.209m loss of KE = 4.739m = 9.147*10^4 J
October 28, 2014

Physics
pressure is force/area force is equal to weight, so (a)
October 28, 2014

sci
as are all theories, (a) It has, in fact, changed several times already.
October 28, 2014

math
C = kn
October 28, 2014

math
it's the fractional part of a decimal number. .123 is the mantissa of 61.123 It is often used when describing logarithms base 10. If the mantissa is .3010 log 2 = 0.3010 log 20 = 1.3010 log 200 = 2.3010 the mantissa provides the basic number, from 1 to 10. The ...
October 28, 2014

math
well, 108/1.2 = 90
October 28, 2014

physics
to balance, m1 x1 = m2 x2 so, (50.0)(1.90) = (45.0)(x2) cinchy, right?
October 28, 2014

Math 5 grade - typo?
first problem. The sum of the even digits cannot be an odd number.
October 27, 2014

Math Help..!
63.28 - 27.45 = ?
October 27, 2014

Math
1/x=(x-34)/(2x^2) multiply by 2x^2: 2x = x-34 x = -34
October 27, 2014

Math
If we assume there are 18 fewer walkers than bus riders, and there are 6 walkers, then if we let x be the number of riders, then x - 18 = 6
October 27, 2014

Algebra
slope = -1/3 point-slope form: y+2 = -1/3 (x-4) Now rearrange that into slope-intercept form.
October 27, 2014

math
If $x at 10%, the rest $(1000-x) is at 8%. So, add up the interest .10x + .08(10000-x) = 950
October 27, 2014

math
x/8 = 2x/9 + 1
October 27, 2014

math
consider the % of juice before and after adding x liters of water: .10(5) = .04(5+x)
October 27, 2014

math
if anna's speed is s, then since distance = speed*time, 9s = 9(1.2s)-10 9s = 10.8s - 10 1.8s = 10 s = 5.55 m/s
October 27, 2014

Wording/Vocab
well, reanimate means to bring the dead back to life. In an article on Mary Shelley, it says, "She was familiar with the ideas of using dead bodies for study, the newer theory of using electricity to animate the dead,..." so, while animate is more often used ...
October 27, 2014

math
4/10 -1/5 9/15-1/3 4/12-1/6 find the difference
October 27, 2014

Math
x(.60)(.40)(.30) = 0.50 x = 6.94 The drop the 2nd year is 6.94(.60)(.60) = 2.50
October 27, 2014

math
disagree. odd*odd = odd example: 3*5 = 15 odd numbers have the form 2k+1 where k is an integer. So, two odd numbers multiplied are (2m+1)(2n+1) = 4mn+2m+2n+1 = 2(2mn+m+n)+1 = 2k+1 where k = 2mn+m+n
October 27, 2014

Math
from your handy Z table, you find that 24 is 2/2.1 = 0.952 std above the mean P(Z>0.952) = 0.17 See the app at http://davidmlane.com/hyperstat/z_table.html
October 27, 2014

College algebra
slope (m) = (9-11)/(6-4) = -1 so, y=-x+b y(4)=11, so b=15 y = -x+15
October 27, 2014

math
1+1 = 2 12/20+15/20 = 27/20 -> 2 Hmm. Looks the same to me.
October 27, 2014

math
consider the sum 3/5+3/4. round each fraction and estimate the sum. add the two fraction using a common denominator and then round the result. which estimate is closer to the actual answer.
October 27, 2014

math
if the school record for the softball throw is 78 ft about how much farther must Robert throw the ball to match the record. a 15ft b 16ft c 18 ft d 20ft
October 27, 2014

math
4/8-1/4 find the diffence
October 27, 2014

math
3 1/4 + 2 5/6 estimate each sum or difference
October 27, 2014

Algebra
a square has the max area for a given perimeter.
October 27, 2014

math
9/10-3/5 find the difference
October 27, 2014

Stats
you can play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html It has very nice input forms so you can specify tails or middle regions.
October 27, 2014

Math
Since v = 1/3 pi r^2 h I get v = (1/3)(3.14)(9)(8) = 75.36 How did you get your answer?
October 27, 2014

physics
A small block of mass m = 225 g is released from rest at point circled A along the horizontal diameter on the inside of a frictionless, hemispherical bowl of radius R = 27.5 cm as shown in the figure below. (a) Calculate the gravitational potential energy of the block-Earth ...
October 27, 2014

Algebra, help please!!!
well, clearly, if you want values between 4.30000000000000... and 4.33333333333333... All you need to do is replace the string of zeroes with something less than 33333333333333... So, you could have 4.3123456789 4.3010101010 4.33333322222 Similarly for the other one
October 27, 2014

algebra. help!
|110-30t| = 40 so, either 110-30t = 40 30t = 70 t = 7/3 = 2.3 or -(110-30t) = 40 -110+30t = 40 30t = 150 t = 5 So, (A) is correct
October 27, 2014

algebra. help!
3x+10 >= 4 3x >= -6 x >= -2 (A) 2.25x >= 180 x >= 80 you are correct
October 27, 2014

Calculus: need clarification to where the #'s go
y = 2√(4x+4) = 4√(x+1) THE DISTANCE D IS FOUND USING d^2 = x^2+y^2 = x^2+16(x+1) = x^2+16x+16 when x=3, d=√73 so, 2d dd/dt = (2x+16) dx/dt d dd/dt = (x+8) dx/dt so, now for the numbers: √73 dd/dt = 11(5) dd/dt = 55/√73
October 27, 2014

Pre-Calc/Trig
it depends. as a function of time, or of distance? wikipedia's article on trajectory has many useful equations.
October 27, 2014

Algebra
(2a-b)^3 = (2a)^3 - 3(2a)^2b + 3(2a)b^2 - b^3 = 8a^3 - 12a^2b + 6ab^2 - b^3 better review your binomial coefficients. I think you used 2 instead of 3. the other is correct
October 27, 2014

Math Homework
3x^2+2x > 2x^2-3 x^2 + 2x + 3 > 0 since the discriminant is negative (4-12), this has no real roots. That is, it does not cross the x-axis. Since f(0) = 3 > 0, f(x) is always > 0, so the solution is all real numbers. 4x^2 - x < 0 x(4x-1) < 0 Recall what you ...
October 27, 2014

algebra
Since the domain of f is all x, the range of f(6x) is the same as the range of f(x). The graph is just contracted horizontally by a factor of 6. The range is unaffected. So, the range of g(x) = f(6x)+1 is just [-11,3]+1 = [-10,4] Things would have been stickier had the domain ...
October 27, 2014

Calculus: need clarification to where the #'s go
just use the formula v = 4/3 pi r^3 a = 4pi r^2, so dv/dt = 4pi r^2 dr/dt = a dr/dt da/dt = 8pi r dr/dt v(14) = 11494 a(14) = 2463 So, we have 80 = 2463 dr/dt da/dt = 8pi(14)(80/2463) = 11.43
October 27, 2014

Algebra
Hmm. I get 2x(3x^2-4xy+2y^2) + 5y(3x^2-4xy+2y^2) = 6x^3 - 8x^2y + 4xy^2 + 15x^2y - 20xy^2 + 10y^3 = 6x^3 + 7x^2y - 16xy^2 + 10y^3
October 27, 2014

algebra--1 question
Just use >= for greater than or equal Your solution is correct. x < -3 or x >= 5
October 27, 2014

algebra 2
He only falls 1500 ft before the chute opens. So, change d to 1500 in the above solution and then rework the numbers.
October 27, 2014

Calculus: need clarification to where the #'s go
you have your formula: pv^1.4 = c, so you get v^1.4 dp/dt + 1.4pv^.4 dv/dt = 0 Now just plug in your numbers: (330^1.4)(-10) + (1.4)(330^.4)(79) dv/dt = 0 -33567.54 + 1125.02 dv/dt = 0 dv/dt = +29.84
October 27, 2014

Calculus
To find the rate of increase, note that the distance x after t hours is given by x^2 = (50+19t)^2 + (24t)^2 At 3 pm, t=3, and we have x^2 = 117^2 + 72^2 = 16633 x = 137.4 Now we have to find the derivative: 2x dx/dt = 38(50+19t)+48(24t) = 1874t + 1900 So, at t=3, we have 2(137...
October 27, 2014

science-gen chem
.969g CaCl2 = 0.00873 moles 1.111g KIO3 = 0.00519 moles Each mole of CaCl2 requires 2 moles of KIO3, so clearly the KIO3 is the limiting reagent. So, since each mole of KIO3 produces 1/2 mole of Ca(IO3)2, we get 0.00269 moles of Ca(IO3)2 = 1.051g
October 27, 2014

Calculus - PLEASE HELP!
3√(x^2+y^2) * (x + yy') = (x+yy')/√(x^2+y^2) + 1 x+yy'(3√(x^2+y^2) - 1/√(x^2+y^2) = 1 y' = (1/(3√(x^2+y^2) - 1/√(x^2+y^2) - x)/y y' = [x+√(x^2+y^2) - 3x(x^2+y^2)]/(y(3(x^2+y^2)-1)) So, we want either the numerator ...
October 27, 2014

Calculus
draw a diagram. Let the distance from the pole be x, and the shadow's length be s. Using similar triangles, we have s/6 = (x+s)/15 or, 5s = 2x+2s 3s = 2x so, ds/dt = 2/3 dx/dt plug and chug
October 27, 2014

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

Search
Members