how dyu expand c brakets (x + 3)(x + 1)(x – 2)?

(x + 3)(x + 1)(x - 2)
= (x*x + 3*x + 1*x + 3*1)(x - 2)
= (x^2 + 3x + x + 3)(x - 2)
= (x^2 + 4x + 3)(x - 2)
= x^2*x + 4x*x + 3*x - x^2*2 - 4x*2 - 3*2
= x^3 + 4x^2 + 3x - 2x^2 - 8x - 6
= x^3 + 4x^2 - 2x^2 + 3x - 8x - 6
= x^3 + 2x^2 - 5x - 6

(x+a)(x+b)(x+c) = x^3 +(a+b+c)x^2 +(ab+bc+ca)x + abc.
Take care of +ve and -ve signs of a, b and c.