avem formula (a+b)²=a²+2ab+b²
(a-b)²=a²-2ab+b²
(2x-3y)²=(2x)²-2×2x×3y+(3y)²=4x²-12xy+9y²
(3a+5b)²=(3a)²+2×3a×5b+(5b)²=9a²+30ab+25b²
(√3x-√2x²)=(√3x)²-2×√3x×√2x+(√2x)²=3x²-2√6x²+2x²=x²-2√6x²
(1/3a+2x)²=(1/3a)²+2×1/3a×2x+(2x)²=1/9a²+4x/3a+4x²
(√3+3b)²=(√3)²+2×√3×3b+(3b)²=3+6√3b+9b²