Friday

October 21, 2016
Total # Posts: 45,129

**Calculus integrals**

I'd start with a long division. The integrand then becomes 8 - 3e^x + e^(2x) - 8/(e^x+1) 8 - 8/(e^x+1) = e^x/(e^x+1) if you let u = e^x+1 du = e^x dx and the integrand is now -3e^x + e^(2x) - 8du/u making the integral -3e^x + 1/2 e^(2x) - 8log(e^x+1) + C

*October 18, 2016*

**math**

draw the triangles in standard position. They are all either 45-45-90 of 30-60-90. Those values you know, right?

*October 18, 2016*

**Maths**

In general, of course, three curves need not intersect in a single point. But, as you say, 2x^2+5x = x^2+4x+12: x = -4 or 3 2x^2+5x = 3x^2+4x-6: x = -2 or 3 x^2+4x+12 = 3x^2+4x-6: x = -3 or 3 So, it looks like (3,33) works fine You messed up in your solution. 6*5 = 30, not 12...

*October 18, 2016*

**MATH PLEASE SHOW WORK**

what work? If the smallest is x, then the next two are x+2 and x+4. So, x^2 + (x+2)^2 = 54+20(x+4) Now just crank it out.

*October 18, 2016*

**Math**

there are many many possibilities. What topic are you studying just now?

*October 18, 2016*

**math please help**

see related questions below

*October 18, 2016*

**math**

pick any number. Multiply top and bottom by that number. For example, 3/30 .17/1.7 and so on

*October 18, 2016*

**Math**

well, 8 + 7 = 15

*October 18, 2016*

**Algebra**

45 is 3/4 of the way from 30 to 50, so 3/4 of the mix will be 50%. Or, more traditionally, 30x + 50y = 45(x+y) 30x + 50y = 45x + 45y 5y = 15x y = 3x So, there is 3 times as much 50% as 30%.

*October 18, 2016*

**Math**

.5*1000 + .25x = 900

*October 18, 2016*

**Mathematics**

(b+5)/(b+2) = 5/4 ...

*October 18, 2016*

**Math**

4/3 * 7/2

*October 18, 2016*

**Math**

no, that's 90% You want .55*120 - .45*120 = 0.10*120

*October 18, 2016*

**Math**

it won 10% more. What is 10% of 120?

*October 18, 2016*

**Math**

P = 2(W+L)

*October 18, 2016*

**Math**

well, 14*3 = 42

*October 18, 2016*

**math**

#7 Nope. The total key sales must be >= 180K #8 Nope. 85 <= (83+91+x)/3 <= 90 #9 Nope. |105 - 35t| = 60 105 - 35t = ±60 #10 First of all, P is not a subset of V. So you are naming the wrong symbol. Your answer appears to be P-V (elements of P not in V) (a) = P...

*October 18, 2016*

**MATH**

No ideas? OK. I'll get you started. As usual, with a diagram. Let's set some labels: S = top of short pole T = top of tall pole C = cable car P = point on ground directly below the car Draw a horizontal line from C which intersects the short and tall poles at Q and R, ...

*October 18, 2016*

**pyhsics**

PE = mgh h = 900-60t

*October 18, 2016*

**Math**

(1-x)/(x-5) + 7x / (x-5)(x+2) ((1-x)(x+2)+7x) / (x-5)(x+2) -(x^2-6x-2) / (x^2-3x-10) Generally one does not talk about "factoring" rational functions. Maybe there was some other operation you had in mind.

*October 18, 2016*

**Physics trajectory**

4.9t^2 = 4.5

*October 18, 2016*

**Math please help**

x^2 + (x+2)^2 = 54+20(x+4)

*October 18, 2016*

**Math**

The sides are 9x and 7x. 2(9x+7x) = 144

*October 18, 2016*

**Math please help**

h(h+1)/2 = 10

*October 18, 2016*

**Math**

jeez! enough with the same problem, already!

*October 18, 2016*

**Math**

adjacent angles add to 180

*October 18, 2016*

**MATH**

Well, I made a boo-boo. Clearly you did not bother to read my work, or you would have found it. I was just as blind, because if the glass empties 10 in. in one hour, clearly the .15 in/hr I got for an answer was way too small. So, it all goes back to this: I swapped y and r in...

*October 18, 2016*

**MATH**

So, what did you try? It'd be nice if you showed your work on the problem. http://www.jiskha.com/display.cgi?id=1476782673

*October 18, 2016*

**Math**

it has decreased by a factor of 3/4 So, it must increase by a factor of 4/3, or up by 33.33%

*October 18, 2016*

**Algebra**

(1-2+4)z + 6

*October 18, 2016*

**math**

just solve x+8 + x+4 + 4x-3 + x^2-3x = 49

*October 18, 2016*

**MATH**

When the man has walked a distance x, his distance d from the pole is d^2 = x^2+30^2 If his shadow then has length s, s/6 = (d+s)/126 or, d = 20s So, plugging that in, 400s^2 = x^2+30^2 at x=40, s = 5/2 800s ds/dt = 2x dx/dt 2000 ds/dt = 80*3 ds/dt = 3/25 When you get stuck, ...

*October 18, 2016*

**Calc**

ok ok I did the first two. See what you can do on these, ok?

*October 18, 2016*

**Maths**

I suspect a typo. There is a mangled character.

*October 18, 2016*

**math**

pi * 2.5

*October 18, 2016*

**Math**

come on. If you are x, what is 5 more than that? what is 5 more than 10? How did you get it? Do the same with x.

*October 18, 2016*

**physics (urgent)**

Read the excellent article at wikipedia: https://en.wikipedia.org/wiki/Trajectory You can then understand why max height = (v sin^2θ)/2g range = (v^2 sin2θ)/2g time in air solves (v sinθ) t - g/2 t^2 = 0

*October 18, 2016*

**math**

The terms grow by 7, so (6293-14)/7 + 1

*October 18, 2016*

**math**

this is just 2(1+2+...+400) So, there are 400 terms. S400 = 400/2 (2+800) Or, you probably know that 1+2+3+...+n =n(n+1)/2 So, your sum is 2* 400*401/2

*October 18, 2016*

**math**

see your other posts. Or, review your material on arithmetic sequences...

*October 18, 2016*

**CALC**

consider the lamina as a collection of thin vertical strips, of height y and width dx. Just add up all the masses. Each strip's mass is its area times it density. If we integrate along x, the density is a constant for each strip. m = ∫[0,1] ρ y dx = ∫[0,1...

*October 18, 2016*

**CALC**

Hmmm. I have to run, but maybe you can figure it out by the time I get back.

*October 18, 2016*

**CALC**

Consider the area as a bunch of tiny rectangles, each of width dx and height dy. Each rectangle's mass is its area times its density. o, adding them all up, using vertical strips so we don't have to split the boundary: m = ∫R ρ dy dx = ∫[0,3]∫[x/...

*October 18, 2016*

**Calculus**

google is your friend. Take a look here: http://mathhelpboards.com/questions-other-sites-52/leprofeces-question-yahoo-answers-minimizing-lateral-area-cone-fixed-volume-8554.html

*October 18, 2016*

**Math**

2 7/12 + 1 5/7 = 2 49/84 + 1 60/84 = 3 109/84 = 4 25/84

*October 18, 2016*

**Math**

equilibrium quantity is where supply = demand: -2x+15 = 5x+1 x = 2 so, p=11 Looks like D to me

*October 18, 2016*

**Math help**

just solve C(x) = R(x) ...

*October 18, 2016*

**math**

425

*October 18, 2016*

**Maths**

c'(x) = 40 + 0.4x c(x) = 40x + 0.2x^2 + k Now plug in your known value of c(0) = 600 c(x) = 600 + 40x + 0.2x^2

*October 18, 2016*

**Differentiation**

yes

*October 18, 2016*

**math**

see http://www.jiskha.com/display.cgi?id=1476803497

*October 18, 2016*

**math**

I have that formula because, as I showed at the very first, the volume starts at 30π ion^3, and drops at a rate of π/2 in^3/min. ----------------------------------- For those who followed a link to get here, ----------------------------------- I swapped y and r in ...

*October 18, 2016*

**math**

v = π/3 * 3^2 * 10 = 30π so, dv/dt = -30π in^3/hr = -π/2 in^3/min When the sand has a depth of y inches, the surface has a radius of r = (3/10) y So, at that point, v = π/3 y^2 r = π/10 y^3 dv/dt = 3π/10 y^2 dy/dt -π/2 = 3π/2 * 6^2 ...

*October 18, 2016*

**Maths**

.24x = 16.2

*October 18, 2016*

**physics - oops**

rats: 5t^2=20

*October 18, 2016*

**physics**

how long does it take to hit the ground? 10t^2 = 20 use that t to find the horizontal distance: d = 15t.

*October 18, 2016*

**MATH**

divide the nut into 6 equilateral triangles, with sides = r. y=r

*October 18, 2016*

**math**

If the ladder has length z, then x^2+y^2 = z^2 x dx/dt + y dy/dt = 0 when dy/dt = -3 dx/dt, x dx/dt - 3y dx/dt = 0 x = 3y Thus, the angle θ is tanθ = 1/3

*October 18, 2016*

**math**

I'll assume you meant that the faster plane is 5 miles farther east... say the slow one is flying along the x-axis, and the faster one along the line y=12. Then at time t hours, the distance z between them is z^2 = (300t - 240t)^2 + 12^2 = 3600t^2 + 144 300t-240t = 5 when ...

*October 18, 2016*

**algebra**

If the regular gas costs x cents/gal, then 5x + 10(x+22) = 6130

*October 18, 2016*

**Please explain**

if you rearrange things a bit, you get 7x-3y = 63 2x+4y = -42 Looks like A to me.

*October 17, 2016*

**PRE-CAL**

cot^2 = csc^2 - 1 use that and it factors easily.

*October 17, 2016*

**6th grade math**

Not really. Draw a figure with any number of sides. Except for a triangle, it can be squashed in various ways, making the area anything from almost zero to a maximum when the figure is a regular polygon. That is why structures are usually based on triangular frameworks -- the ...

*October 17, 2016*

**math**

If there are x liters of the 55%, then the rest (50-x) is 80%. SO, now just add up the acid in the parts -- it must equal the acis in the final mix: .55x + .80(50-x) = .60*50

*October 17, 2016*

**Trig**

I assume you meant (using x) sin3x - sin4x Use the sum-to-product formula: sinA-sinB = 2 cos(A+B)/2 sin(A-B)/2

*October 17, 2016*

**2nd grade math**

1100 1121 1142 1163 1184

*October 17, 2016*

**Calculus**

Consider the function y = -x^2

*October 17, 2016*

**Math**

combine the three heights into a single height. How about some input on your other posts? It begins to look like a homework dump, since most of the problems are very similar.

*October 17, 2016*

**Mathematics**

I get 2 2/5 How did you do it?

*October 17, 2016*

**Math**

I'd say the population, since that is what she's measuring.

*October 17, 2016*

**Mathematics**

that is a line

*October 17, 2016*

**Math**

clearly they are using x as an operator, and not a variable. Always better to use * online: 4*(6-5) = 4*1 = 4

*October 17, 2016*

**Math**

or, 5 4/16 + 2 9/16

*October 17, 2016*

**Geometry**

x = (180-x)/3 - 20 I guess. Your language is garbled.

*October 17, 2016*

**6th Grade Math**

round down and round up 7+31+6 < sum < 8+32+7

*October 17, 2016*

**maths**

or, just remember that s = rθ = 5/2 * 8 = 20

*October 17, 2016*

**Trig**

Looks like tan 2T to me

*October 17, 2016*

**Math**

x-1 + x + x+7 = 69

*October 17, 2016*

**maths need steve**

Hmmm. Maybe you mean x+y+z = 4 xy + xz + yz = 5 xyz = 6 Since that has no real solutions, I don't think that's what you meant.

*October 17, 2016*

**Geometry**

no idea what the angles are. if they are alternate interior or exterior, then that is enough.

*October 17, 2016*

**science**

the farther/slower one

*October 17, 2016*

**Geography**

induced them to move to Miami!

*October 17, 2016*

**Math Functions**

S(x) = 4.00 + 1.50x Now that wasn't so hard, eh?

*October 17, 2016*

**Math**

x/3 = 24

*October 17, 2016*

**math**

fix typos.

*October 17, 2016*

**Math**

all correct.

*October 17, 2016*

**math**

the smaller is 1/20 * 94.6

*October 17, 2016*

**Algebra**

when multiplying add powers. when dividing, subtract powers. So, you have (6.0×10^-5)×(3.0×10^4) = (6.0*3.0)x10^(-5+4) = 18.0x10^-1 but that is not scientific notation. You have to shift the decimal point so you get 1.8x10^0 = 1.8 I suspect you have garbled ...

*October 17, 2016*

**Calculus**

Just because the graph is constant, that does not mean that f = 0.

*October 17, 2016*

**geometry**

That's what Jiskha is for - helping students in trouble! The locus is the perpendicular bisector of the line segment joining the two points. In this case, the y-axis!

*October 17, 2016*

**Can you say "TestPost"?**

eh?

*October 17, 2016*

**Algebra 2**

y = 1/(2x-10) - 3 = 1/(2(x-5)) - 3 = (1/2) * 1/(x-5) - 3 Now can you see the scaling and shifting?

*October 17, 2016*

**Algebra2**

clearly, xy=10 that's inverse variation.

*October 17, 2016*

**Math**

I have also seen this referring to 0.57 meaning a repeating decimal. In that case, 0.57 = 57/99 because if x = 0.57 100x = 57.57 now subtract and the .57 part goes away and you are left with 99x = 57

*October 17, 2016*

**Maths**

are you missing some parentheses?

*October 17, 2016*

**Math**

reposting after only 7 minutes? Impatient much? See your earlier psting.

*October 17, 2016*

**Math Help**

each year, 1/5 of lost value (10800-18000) is subtracted. Or, note that 18K is 1/6 of 108K. That is, in 5 years it has lost 5/6 of its value: 1/6 per year.

*October 17, 2016*

**Math**

express all fractions with a denominator of 6, and it becomes quite clear. Just look at the numerators.

*October 17, 2016*