Question

If 3x + 2/x = 7, then 9x^2-4/x^2=​

Answer 1

Answer:

$3x + \frac{2}{x} = 7 \\ 3 {x}^{2} + 2 = 7x \\ 3 {x}^{2} - 7x + 2 = 0 \\ \\ 3 {x}^{2} - 6x - x + 2 = 0 \\ 3x(x - 2) - 1(x - 2) = 0 \\ (3x - 1)(x - 2) = 0 \\ x = \frac{1}{3} or \: 2 \\ 9 {x}^{2} - \frac{4}{ {x}^{2} } \\ = 9 \times {( \frac{1}{3}) }^{2} - \frac{4}{ ( { \frac{1}{3}) }^{2} } \\ = 9 - 36 \\ = - 27 \\ or = 9 \times {2}^{2} - \frac{4}{ {2}^{2} } \\ = 36 - 1 \\ = 35$