Помогите срочно решить

Ответ:

$1)a)(2a - 3b) { \:}^{2} = \\ = 4a {}^{2} - 6ab - 6ab - 9b {}^{2} = \\ = 4a {}^{2} - 12ab + 9b {}^{2}$

$b)(5x - 3y)(5x + 3y) = \\ = 15x {}^{2} + 15xy - 15xy - 9y {}^{2} = \\ = 15x {}^{2} - 9y {}^{2}$

$c)2a {}^{3} (a + 2b) {}^{2} = \\ = 2a {}^{3} (a {}^{2} + 4ab + b {}^{2} ) = \\ = 2a {}^{5} + 8a {}^{4} b + 2a {}^{3} b {}^{2}$

$2)a)25a {}^{2} - 16 = \\ = 5 {}^{2} a {}^{2} - 4 {}^{2} = \\ = (5a) {}^{2} - 4 {}^{2} = \\ = (5a - 4)(5a + 4)$

$b) - 3x {}^{2} + 6x - 3 = \\ = - 3(x {}^{2} + 2x - 1) = \\ = - 3(x - 1) {}^{2}$

$c)8x {}^{3} + y {}^{3} = \\ = (2x) {}^{3} + y {}^{3} = \\ = (2x + y)(4x {}^{2} - 2xy + y {}^{2} )$

$d)4x {}^{2} + 9y {}^{2} - 12xy = \\ = (2x - 3y) {}^{2}$

$3)4a {}^{2} - 9 = 0 \\ 4a {}^{2} = 9 \\ a {}^{2} = \frac{9}{4} \\ a = + - \sqrt{ \frac{9}{4} } \\ a = + - \frac{3}{2}$