Question

Solve the equation `2x - 1/x = 7` and determine the answer correct to two decimal places.

Answer 1

Given:

`2x - 1/x = 7`

Multiply both sides by x (x ≠ 0): 

`=> 2x^2 - 1 = 7x `

`=> 2x^2 - 7x - 1 = 0`

`x = [7 ± sqrt(49 + 8)] / 4`

`= (7 ± sqrt57)/4`

Numerically: √57

= 7.549834435

`x1 = (7 + sqrt57)/4`

= 3.6374586088

= 3.64

`x2 = (7 - sqrt57)/4`

= −0.1374586088

= −0.14

So x = 3.64 or x = −0.14