a. (2a+3b)x(2a-3b)=
Avem formula de calcul : (a+b)x(a-b)=a²-b²
(2a+3b)(2a-3b)=(2a)²-(3b)²=4a²-9b²
b. (4x²+2y²)(4x²-2y²)=
(a²+b²)(a²-b²)=(a²xa²)(a²x-b²)(b²xa²)(b²x-b²)
(4x²+2y²)(4x²-2y²)=(4x²x4x²)(4x²x-2y²) (2y²x4x²)(2y²x-2y²)=16x⁴-8xy⁴+8xy⁴-4y⁴=16x⁴-4y⁴
c. [tex](2 \frac{1}{2} x+ \frac{3}{4} y)(2 \frac{1}2x- \frac{3}{4}y )= ( 2 \frac{1}{2}x
) ^{2} -( \frac{3}{4}y) ^{2} [/tex]
d. (0.2x+0.5y)(0.2x-0.5y) =
(a+b)(a-b)=a²-b²
(0.2x+0.5y)(0.2x-0.5y)= 0.2x²-0.5y²
