Giải toán 8 tập 1: Câu 78 sgk trang 33

a) \((x + 2)(x - 2) - (x - 3)(x + 1)\)
\(= x^2 - 2^2 - (x^2 + x - 3x - 3)\)
\(= x^2 - 4 - x^2 - x + 3x + 3\)
\(= 2x - 1\)
b) \((2x + 1)^2 + (3x - 1)^2 + 2(2x + 1)(3x - 1)\)
\(= (2x + 1)^2 + 2.(2x + 1)(3x - 1) + (3x - 1)^2\)
\(= [(2x + 1) + (3x - 1)]^2\)
\(= (2x + 1 + 3x - 1)^2\)
\(= (5x)^2 \)
\(= 25x^2\)