Question

(X+1)(X+2)(X+3)(X+4)简便方法

Answer 1

=[(X+1)(X+4)]*[(X+2)(X+3)]=(X^2+5X+4)(X^2+5X+6)=(X^2+5X)^2+10*(X^2+5X)+24

更炫的 = (X^2+5X+4)(X^2+5X+6) =(X^2+5X+5 - 1)(X^2+5X+5 + 1)=(X^2+5X+5)^2 - 1

全部展开 = x^4 + 10x^3+ 35x^2 + 50x + 24