A) (3a-b)(3a+b)+b^2= 9a^2 - 3ab + 3ab - b^2 + b^2= 9a^2
б) 9x^2 - (y+4x)(y-4x)= 9x^2 - (y^2 - 4xy + 4xy - 16x^2)= 9x^2 - y^2 + 16x^2= 25x^2 - y^2
в) (5с-6d)(5c+6d)-25c^2= 25c^2 - 30cd + 30cd - 36d^2 - 25c^2= -36d^2
г) 7d^2(d-1)(d+1)= 7d^2(d^2 - 1)= 7d^4 - 7d^2
A) (3a-b)(3a+b)+b^2
= 9a^2 - 3ab + 3ab - b^2 + b^2
= 9a^2
б) 9x^2 - (y+4x)(y-4x)
= 9x^2 - (y^2 - 4xy + 4xy - 16x^2)
= 9x^2 - y^2 + 16x^2
= 25x^2 - y^2
в) (5с-6d)(5c+6d)-25c^2
= 25c^2 - 30cd + 30cd - 36d^2 - 25c^2
= -36d^2
г) 7d^2(d-1)(d+1)
= 7d^2(d^2 - 1)
= 7d^4 - 7d^2