# Posts by Steve

Total # Posts: 49,732

**math NEED HELP ASAP**

.60x + 1.00(120-x) = .70*120

*March 6, 2017*

**Calculus**

either 5+2/x < 1 or -(5+2/x) < 1 In the first case, x is in (-1/2,0) In the 2nd case, x>0 or x < -1/3 . . .

*March 6, 2017*

**Math**

so, just solve for d when -0.02d^2+2.6d-66.5 = 0

*March 6, 2017*

**Math**

#1 y = (3/4)x+b 7 = (3/4)*4+b b=4 so, y = (3/4)x+4 Clearly (0,0) does not satisfy that equation #2 x/y can be zero if x=0 Only y cannot be zero. #3 ok #4 volume is always in cubic units. Area is square units. #5 85+92+80+90+x = 5*89 x = 98 How could you possibly believe such a...

*March 6, 2017*

**math**

do the () first 10-7=3 3 squared=9 4 times 9 =36 36 times 7 =252 252+4=256

*March 6, 2017*

**math**

subtract the 25 from 14

*March 6, 2017*

**math**

15+19=34 34-6=28 28/2=14 14-25=negative 11

*March 6, 2017*

**Algebra2**

thank you very much

*March 6, 2017*

**Algebra2**

find a quadratic function in standard form for each set of points. (-1,2),(0,1),(1,-4)

*March 6, 2017*

**mathemadics**

come on. Take a stick and break it into thirds. How many pieces are there?

*March 6, 2017*

**math**

at 3 m/s, time t: 3t time t+1: 3(t+1) = 3t+3

*March 6, 2017*

**Math**

coconut: (3/5)(1/3) = 1/5 angel: (2/5)(1/6) = 1/15 assuming no cakes are coconut ... If all the cakes are either coconut or angel food, then coconut: (3/5)(1/3) + (2/5)(5/6) = 8/15

*March 6, 2017*

**Algebra**

how about 7*2*9 ?

*March 6, 2017*

**Algebra**

2 legs per animal yields 26 legs There are 6 extra legs, so what does that say? Think about what happens when you replace a chicken with a sheep.

*March 6, 2017*

**Calculus**

Too bad you didn't show your work... f' = 1 + 2cosx f'=0 when cosx = -1/2 x = 2?/3, 4?/3 f" = -2sinx f"(2?/3) < 0, so that is a maximum f"(4?/3) > 0, so that is a minimum See the graph at http://www.wolframalpha.com/input/?i=x%2B2sinx,+for+x+%...

*March 6, 2017*

**Math**

m = kh now plug in your numbers

*March 6, 2017*

**Math**

a:b = 3:8 b:c = 1:6 = 8:48 a:b:c = 3:8:48 a:c = 3:48 = 1:16

*March 6, 2017*

**Math**

no idea what the shaded region is.

*March 6, 2017*

**Algebra**

plot each line and the solution is where they intersect.

*March 6, 2017*

**math 73**

add up the amount of fat in the milk and cream. It must equal the amount in the mix. If there are x gallons of cream, then the rest (20-x) is milk. So, .22x + .02(20-x) = .04(20)

*March 6, 2017*

**Geometry**

2(w+78) = 260

*March 6, 2017*

**maths curve need help**

First step: draw the graphs! They intersect at (0,0) and (1,1). You want to rotate a small lens-shaped area. To find the volume, you can do two methods. Think of the volume as a stack of discs with holes (washers). The holes are there because a slice of area is rotated around ...

*March 6, 2017*

**Math**

#1 #2 are ok the volumes are in the cube of the linear ratio. So, v' = (10/15)^3 v = 8/27 v = 160 This is due to the fact that each dimension scales the same way. In the case of the sphere, replace r by (2/3)r in the formula. Then you get v = 4?/3 r^3 v' = 4?/3 (2/3 r...

*March 6, 2017*

**Algebra2**

a = a1 = 2*1-3 = -1 d = an+1-an = (2(n+1)-3)-(2n-3)) = 2 Now just use your sum formula S10 = 10/2 (2a+9d)

*March 6, 2017*

**Algebra2**

What is the sum of the first 10 terms of the sequence defined by an = 2n - 3?

*March 6, 2017*

**Math**

good start, but 16 years means 32 payments.

*March 6, 2017*

**physics**

recall that the index n is defined by n = c/v

*March 6, 2017*

**Calculus**

I assume a triangular cross-section. So, the width of the water surface when it has a depth of y is y/2. Thus the volume of water of depth y is v = (1/2)(y)(y/2)(8) = 2y^2 dv/dt = 4y dy/dt Now just plug in your numbers

*March 6, 2017*

**math**

same as for any regular n-gon: area = 1/2 perimeter * apothem But it will be very close the the circle.

*March 6, 2017*

**Trig**

well, (u-3)(u+1)/(u+1) = u-3 as long as u ? -1

*March 5, 2017*

**Algebra**

yes

*March 5, 2017*

**Algebra**

don't you recognize 8^2 and 9^2 ?

*March 5, 2017*

**Maths**

2(5x+3x) = 128 x = 8 so, ...

*March 5, 2017*

**Algebra**

well, 32 = 2^5 that should help

*March 5, 2017*

**Calculus**

e^(ax) = e^(a/b * bx) = (e^(a/b))^(bx) C = e^(a/b)

*March 5, 2017*

**Calculus**

If I read all those words correctly, you mean ?[-3,3] f(x) dx where f(x) = f1: ?(4-?(x+1)) for -3 <= x <= 1 f2: |x-2|-1 for 1<x<3 Unfortunately, for x < -1 the first piece is complex, not real. Anyway, fix the presumed typo and just plug in the pieces ?[-3,1] f1...

*March 5, 2017*

**math**

Draw the figure. If the height is h, then you have a 40-by-h rectangle in the center, with extra lengths of x and 25-x on the longer base. x^2+h^2 = 56^2 (25-x)^2+h^2 = 39^2 x^2-56^2 = (25-x)^2 - 39^2 x = 224/5 so, h^2 = 56^2-x^2 = 28224/25 h = 168/5 so, the area is (40+65)/2...

*March 5, 2017*

**Math/Calculus**

Consider the set of nested shells of thickness dy. v = ?[0,4] 2?rh dy where r=y and h=218-x = (y+2)^3+2 v = ?[0,4] 2?y(218-((y+2)^3+2)) dy = 8192?/5 as a check, using discs of thickness dx, v = ?[10,218] ?r^2 dx where r=y=(x-2)^(1/3)-2 v = ?[10,218] ?((x-2)^(1/3)-2)^2 dx = ...

*March 4, 2017*

**Calculus**

assuming you mean 1<=x<=5, we have, using discs, v = ?[1,5] ?(R^2-r^2) dx where R=x^(1/5) and r=(x/5)^2

*March 4, 2017*

**Calculus**

each triangle at a distance x from (0,0) has a base of 2y = 2?(64-x^2) So, the total volume, taking advantage of symmetry is v = 2?[0,8] bh/2 dx = 2?[0,8] 2?(64-x^2)*2?(64-x^2)/2 dx = 4?[0,8] (64-x^2) dx = 4096/3

*March 4, 2017*

**Calculus**

Find the volume of the solid whose base is the circle x^2+y^2=64 and the cross sections perpendicular to the x-axis are triangles whose height and base are equal. Find the area of the vertical cross section A at the level x=7.

*March 4, 2017*

**calculus**

h^2 = 6^2 + x^2 h dh/dt = x dx/dt when h=10, x=8, so just plug in the numbers 10 dh/dt = 8*2 dh/dt = 8/5 m/s

*March 4, 2017*

**math**

The only way I can make sense of what you wrote is to interpret it as p = mq^3 q = nr^2 p = m(nr^2)^3 = mn^3 r^6 = kr^k p varies directly as the 6th power of r.

*March 4, 2017*

**Calculus AP Exam review explanation pls**

#1. Recall that the average value is 1/? ?[-?,0] 3^cos(x) dx use your calculator to find that the integral is 4.16348 Divide that by ? and you get 1.32528 #2 is just another integral. Just as distance is ? v(t) dt, here the total change in momentum is ? cost dt since ? p = F ?...

*March 4, 2017*

**Algebra 2**

correct

*March 4, 2017*

**math**

35/60 of the circumference of a complete circle of radius 6 cm.

*March 4, 2017*

**math**

The distance between pencil centers on each side is 1 diameter, or 7mm. At each corner there is a quarter-circle, so the entire length is 4*7 + ?*7 = 7(4+?) mm

*March 4, 2017*

**math**

Draw the diagram, with two congruent triangles at the ends. Notice that the two right triangles are 6-8-10.

*March 4, 2017*

**science**

that means that 90% remains, so (1/2)^(t/1590) = 9/10 t = 241.7 years

*March 4, 2017*

**maths**

h/4 = tan45°

*March 4, 2017*

**math**

(2(3x+100)+100)/4 - x/2 = ?

*March 3, 2017*

**math**

x/y = a/b (x+y)/y = x/y + 1 = a/b + 1 = (a+b)/b the rest follows

*March 3, 2017*

**math**

let's say that for each ounce of 5-cent rice, you buy k ounces of 6-cent rice. 7(1+k) = (5+6k)(6/5) k = 5

*March 3, 2017*

**calculus**

h' = 3/20 ?x the length of cable is s = 2?[0,20] ?(1+h'^2) dx = 2?[0,20] ?(1+9x/400) dx = 44.2 ft Now figure the weight.

*March 3, 2017*

**Calculus**

dy/(y-2) = x^4 dx ln(y-2) = x^5/5 + ln(c) y-2 = c e^(x^5/5) y(0)=0, so c=-2. y = 2-2e^(1/5 x^5) I suspect you did ln(y-2) = x^5/5 + c y-2 = e^(x^5/5) + c That still does not give your answer. Too bad you didn't show your work ...

*March 3, 2017*

**Calculus**

correct. I'd probably have written it y = 1/16 (x^2 + 11)^2

*March 3, 2017*

**Algebra**

It moved 60° in 10 minute. 11:00 t0 11:40 is 40 minutes. 4 times as long, 4 times as many degrees: 240°

*March 3, 2017*

**chemistry**

10/3 the volume, 3/10 the concentration.

*March 3, 2017*

**chemistry**

0.1L * 0.1M = 0.01 moles Now just convert that to grams.

*March 3, 2017*

**Algebra**

Assuming f is quadratic, start with y = (x-2)(x-4) y(3) = -1 So, multiply it by 2 and you have y = 2(x-2)(x-4) = 2(x-3)^2 - 2

*March 3, 2017*

**Algebra**

many functions meet those criteria, but one of them is given roots: y = (x - (1+?2))(x-(1-?2)) = x^2-2x-1 That has a y-intercept of -1. So, multiply it by 4. It has the same roots, but now y(0) = -4.

*March 3, 2017*

**MATHEMATICS**

correct.

*March 3, 2017*

**Algebra 2**

the y-intercept has noting to do with the asymptotes. Unless the asymptote is the y-axis, in which case there is no y-intercept.

*March 3, 2017*

**Mathematics**

4 painters paint 1 room in 12/3 = 4 hours 1 painter paints 1 room in 4/4 = 1 hour Now you can answer the questions.

*March 3, 2017*

**Math**

too bad you couldn't be bothered to show your work. start: $x CD: 18, leaving x-18 dress: half that, leaving x/2 - 9 lunch:11, leaving x/2 - 20 book: 1/3 of that, leaving (2/3)(x/2-20) = x/3 - 40/3 gas: 12, leaving x/3 - 76/3 CD: 1/4 of that, leaving (3/4)(x/3 - 76/3) = x/...

*March 3, 2017*

**Calculus AP Exam review explanation pls**

#1 a = ?[0,3] (3x-x^2) dx = 9/2 #2 Using either discs or shells, v = ?[0,4] ?(2-x)^2 dy = ?[0,4] ?(2-?y)^2 dy = 8?/3 or v = ?[0,2] 2?(2-x)y dx = ?[0,2] 2?(2-x)x^2 dx = 8?/3 #3 I can't make out the function, but the total distance traveled is the arc length of the path ...

*March 3, 2017*

**Math**

the diet looks linear to me. 1/80 lb/day. A cup of coffee cooling is non-linear. The amount of temperature drop depends on the difference in temperature between the coffee and the room. The cooler the coffee gets, the more slowly it cools. Or radioactive decay is non-linear. ...

*March 3, 2017*

**maths binomial expansion**

1/0! x^(1/3) (y/2)^0 + (1/3)/1! x^(-2/3) (y/2)^1 + (1/3)(-2/3)/2! x^(-5/3)(y/2)^2 + (1/3)(-2/3)(-5/3)/3! x^(-8/3)(y/2)^3 + (1/3)(-2/3)(-5/3)(-8/3)/4! x^(-11/3)(y/2)^4 = x1/3 + 1/6 x-2/3 y - 1/36 x-5/3 y2 + 5/648 x-8/3 y3 - 5/1944 x-11/3 y4

*March 3, 2017*

**physics 11**

the horizontal speed is constant. So, how long does it take to fall 36 meters? h(t) = 36 - 4.9t^2 As to the distance of the boat, it depends on the goal: hit or no hit?

*March 3, 2017*

**maths**

v = 4/3 ?r^3 r = ?(3v/(4?)) a = 4?r^2 = 4? * (3v/(4?))^(2/3) = ?(36?v^2) so, for your sphere, a = ?(36?*9000^2) = 900?(4?) ? 2092

*March 3, 2017*

**Math**

6490 * (71/59) = ?

*March 3, 2017*

**Struggling on math please help :(**

just keep adding/subtracting 360° 47+360 = 407+360 = 767° 47-360 = -313 - 360 = -673°

*March 3, 2017*

**Rpcc**

horizontal velocity is constant. vertically after t seconds, v = -9.8t

*March 3, 2017*

**maths trigonometry,**

Always start by finding the reference angle in QI. Then you can work with angles in the standard position (with one corner at (0,0) and lying on the x-axis). tan ?/4 = 1 tan? is positive in QI and QIII so, the solutions are ? = ?/4 and ?+?/4=5?/4 cos ?/3 = 1/2 cos? is negative...

*March 3, 2017*

**maths trigonometry**

(2cos? + 1)(tan? - 1)=0 see your other post, where you have taken the next step.

*March 3, 2017*

**calculus**

as it stands, I think there's something wrong. you want dt/dx = 0 but since ?n is always >= 0, that means that ?(x^2+a^2) + ?(b^2+d^2) = 0 since even powers are always non-negative, that means that x,a,b,d are all zero. and 0 is not in the interval (0,d)

*March 3, 2017*

**calc**

1/f = 1/p + 1/q 0 = -1/p^2 dp/dq - 1/q^2 dp/dq = -p^2/q^2

*March 3, 2017*

**Maths**

same question: how many 1cm cubes does it take to fill a 6cm cube?

*March 3, 2017*

**math**

Since the 30th minute is at the end of the 1st quarter, there is a 3/4 probability that he missed the goal.

*March 2, 2017*

**math**

350.5 is one possible value

*March 2, 2017*

**Calculus**

read the question carefully. v(0) = 3 you want v to be three times its initial value. 3*3 = 9

*March 2, 2017*

**math**

first, 80% interest is too weird to be real. second, I can't quite figure out just what you're asking. Take a look at what you wrote...

*March 2, 2017*

**Calculus**

well, the line has slope 3. So, where does the curve have that slope? y' = 2e^x = 3 x = ln(3/2)

*March 2, 2017*

**maths**

I'd say separation of variables, since you can write it as dy/y^2 = -(t+t^3) dt ------------------------------------------- next is just direct integration, since you already have dy/dt as a function of t. ------------------------------------------- The last is of the form...

*March 2, 2017*

**calculus-snell's law**

try this discussion: http://dev.physicslab.org/Document.aspx?doctype=3&filename=GeometricOptics_LeastTime.xml

*March 2, 2017*

**math**

D because you did not show the data ...

*March 2, 2017*

**math**

actually, since there is only one variable, there is no direct variation. If you meant -4+7x+4 = y then y = 7x is a direct variation.

*March 2, 2017*

**Maths**

using a weekly rate for simple interest, you want p*rt = 1500 50000*(.06/52)t = 1500 t = 26 makes sense, since you will earn 6% of 50000 = 3000 in a year.

*March 2, 2017*

**calculus**

ok, Sam/Maggie, see whether you can set up the needed integrals, and show what you tried.

*March 2, 2017*

**calculus I**

at x=h, the tangent line to the parabola is y - (3-h^2/10) = (-h/5)(x-h) y = -h/5 x + 3+h^2/10 So, find where the line intersects the circle, and find h so that there is only one solution. It might be useful to pick a value of x close to what you expect, and then use an ...

*March 2, 2017*

**geometry**

tan 36° = 0.7265 x^2+y^2 = 25^2 y = 0.7265x x^2 (1 + 0.7265^2) = 25^2 x = 20.2258 p = 2(x+y) = 2(20.2258 + 14.6949) = 69.8414

*March 2, 2017*

**linear approximation**

You want to pick a value of cos(x) where x is near 2?/13, and you know what it is. you know cos(?/6) = ?3/2. 2?/13 = ?/6 - ?/156, which is pretty close to ?/6. cos(2?/13) ? cos(?/6)+(-sin(?/6))(?/156) = ?3/2 - (1/2)(?/156) = 0.8560 the true value is 0.8855 That seems kind of ...

*March 2, 2017*

**calculus**

using shells of thickness dx, and taking advantage of symmetry, v = 2?[0,1] 2?rh dx where r=1-x and h=y=?(1-x) v = 2?[0,1] 2?(1-x)?(1-x) dx = 4??[0,1] (1-x)^(5/4) dx = 16?/9 using discs (washers) of thickness dy, we have v = 2?[0,1] ?(R^2-r^2) dy where R=1 and r=1-x v = 2?[0,1...

*March 2, 2017*

**Math related rates**

if the water depth is h, the radius of the surface is 2/3 h. So, the volume of water is v = 1/3 ?r^2 h = 1/3 ? (2/3 h)^2 h = 4/27 ?h^3 dv/dt = 4/9 ?h^2 dh/dt plugging in the numbers, 3/2 = 4/9 ?*2^2 dh/dt dh/dt = 27/(32?) Too bad you didn't bother to show your work...

*March 2, 2017*

**Algebra 1 - Help!?**

think about it. If a line has a nonzero slope, it extends forever, both left-right and down-up. So, the domain and range are both All Real Numbers. To sketch the graphs, just pick two values for x, figure the corresponding values for y, plot the two points, and draw the line ...

*March 2, 2017*

**maths**

(?*14.642 km)/(50/60 hr) = 55.2 km/hr

*March 2, 2017*

**math**

Your mistake happened early. You said 5x+3y=2 eq.2 X=-3y/5 but really x = (2-3y)/5

*March 1, 2017*

**Precalculus**

it's an exponential function.

*March 1, 2017*