Question

If x+1/x=7, compute x^3+1/x^2

Answer 1

So far I have x^2+1=7x

x^2=7x-1

x^3+1/7x-1

x^2x/(1)+1/(7x-1)

when I cross out 7x-1

i get x+1. then what?

Answer 2

@Hero

Answer 3

Hang on a min.

Answer 4

okay thanks

Answer 5

( x+1)/x=7

multiply both sides by ×

x +1 =7x

Subtract × from both sides

1=6x

x= 1/6

Answer 6

Plug × to other expression

Answer 7

wait so all my x^2+1=7x was incorrect?

Answer 8

. Is the original problem you posted correct as written?

Answer 9

\[x+\frac{ 1 }{ x }=7, x^3+\frac{ 1 }{ x^2 }=?\]

Answer 10

± see, Better you use later to post from now on.

Answer 11

latex *

Answer 12

okay

Answer 13

so does your solution still stand?

Answer 14

@jdoe0001

Answer 15

No, it doesn't

Answer 16

any ideas?

Answer 17

Calculate ( x +1/ x ) ^ 2 and (x+1 / x ) ^ 3 )

Answer 18

i dont get it sorry

Answer 19

one of my friends even said its unsolvable without quadratic formula but im pretty sure my teacher doesnt want a quadratic use

Answer 20

( x + 1 / x ) ^ 2 = 7^2

Answer 21

If you don't get that I can't help you

Answer 22

Expand the left side

Answer 23

\[x^2+\frac{ 1 }{ x^2 }+x+\frac{ 1 }{ x^2 }\]

Answer 24

That's not what I got

Answer 25

lol i give up, i'll ask my teacher tomorrow. thanks

Answer 26

You give up too easy.

Answer 27

Been working on 4 problems for about 2 hours, it's time too move on if I want decently sufficient sleep. I've been getting mixed answers and solutions so I'll just let my teacher explain.

Answer 28

it can be solved with the quadratic formula so I just used that. Not sure if that's what my teacher wants but i'll see.

Answer 29

Nope, it probably isn't. There's another way to solve that your teacher may be looking for.