Question

81x⁴-121x² factorise it

Answer 1

SOLUTION :

$\bf 81x^4 - 121x^2\\\\=(9x^2)^2 - (11x)^2\\ \\=(9x^2+11x)(9x^2-11x)\\\\OR\\\\=( (3x)^2 + 11x)( (3x)^2 - 11x)$

Answer 2

$81x^{4} -121x^{2} = (9x^{2} -11x)(9x^{2} +11x)$