Question

分解因式x的三次方+9x的平方+23x+15

Answer 1

x³+9x²+23x+15

=x³+x²+8x²+8x+15x+15

=x²(x+1)+8x(x+1)+15(x+1)

=(x+1)(x²+8x+15)

=(x+1)(x²+8x+16-1)

=(x+1)[(x+4)²-1²]

=(x+1)(x+4+1)(x+4-1)

=(x+1)(x+5)(x+3)