1) (2a+3b)(2a-3b)=(2a)^2 - (3b)^2=4a^2-9b^2 [ aplicam formula a^2-b^2=(a-b)(a+b) ]
2) (4x^2 + 2y^2) (4x^2 - 2y^2)= (4x^2)2 - (2y^2)^2= 16x^4 - 4y^4
a) 4x^2 - 9y^2= (2x-3y) (2x+3y)
b)1/25a^2 - 9/64b^2= (1/5a - 3/8b) (1/5a+3/8b)
SPER SA TE AJUTE...daca ceva nu iti este clar spune-mi