Question

solve this. please............​

Answer 1

Answer:

$12. \: (x - 5)(x - 7)(x + 4)(x + 6) = 504 = ( - 2) \times ( - 4) \times 7 \times 9$

$x + 6 = 9 \: \: i.e \: \: \: x = 3 \: \: ans.$

$15. \: (x - 1)(x - 2)(x - 3)(x - 4) = 120 = 2 \times 3 \times 4 \times 5$

comparing this we get

$x - 1 = 5 \: \: \: \: so \: \: x = 6 \: \: \: ans.$

$17. \: \: let \: {5}^{x} = y$

$so \: 5y + \frac{5}{y} = 26$

$5 {y}^{2} + 5 = 26y$

$5 {y}^{2} - 26y + 5 = 0$

$5 {y}^{2} - 25y - y + 5 = 0$

$5y(y - 5) - 1(y - 5) = 0$

$(y - 5)(5y - 1) = 0$

$y = 5 \: \: or \: \: \frac{1}{5} = {5}^{x}$

$x = 1 \: \: or \: - 1 \: \: \: \: ans.$