help with Homework

[mathdoc]

Please help solve this:

GIVEN: m+ (1/m) = 3
GIVEN: x = m^2 +(1/m^2)
GIVEN: y = m^3 – (1/m^3)
FIND: x + y

using the first given, by squaring it, I have solved x to be 7
But, I can't find a way to solve the rest.
Please help.
Thanks!

 

[mmm4444bot]

… GIVEN: m+ (1/m) = 3

GIVEN: x = m^2 +(1/m^2)

GIVEN: y = m^3 – (1/m^3)

FIND: x + y

… I have solved x to be 7 Good!

Now, solve the second equation for m.

You'll find four values for m, and these lead to two different values for y, so there are two possible sums for x + y.

(If there's a nifty way to find y directly, similar to how you found x, then I'm not recognizing it right now. Some chow chows are distracting me.)

 

[Deleted member 4993]

Please help solve this:

GIVEN: m+ (1/m) = 3
GIVEN: x = m^2 +(1/m^2)
GIVEN: y = m^3 – (1/m^3)
FIND: x + y

using the first given, by squaring it, I have solved x to be 7
But, I can't find a way to solve the rest.
Please help.
Thanks!

Not too nifty ... but

y = m^3 – (1/m^3) = (m - 1/m)(m^2 +1+1/m^2) = 8(m-1/m)

m = 1/2*(3+y/8) ..............(1)

1/m = 1/2(3-y/8).............(2)

multiply (1) & (2)

3[sup:39youikg]2[/sup:39youikg] - y[sup:39youikg]2[/sup:39youikg]/64 = 4

y[sup:39youikg]2[/sup:39youikg] = 5*64

Continue from here.....