Đáp án:
Giải thích các bước giải:
a) `M(x)=x^2+2x+1`
`⇔ x^2+2x+1=0`
`⇔ x^2+x+x+1=0`
`⇔x(x+1)+x(x+1)=0`
`⇔(x+1)^2=0
`⇔ x=-1`
b) `N(x)=x^2-x-6`
`⇔ x^2-x-6=0`
`⇔ x^2+2x-3x-6=0`
`⇔ x(x+2)-3(x+2)=0`
`⇔ (x-3)(x+2)=0`
`⇔` \(\left[ \begin{array}{l}x=-2\\x=3\end{array} \right.\)
c) `P(x)=2x^2+3x+1`
`⇔ 2x^2+3x+1=0`
`⇔ 2x^2+2x+x+1=0`
`⇔ 2x(x+1)+(x+1)=0`
`⇔ (x+1)(2x+1)=0`
`⇔` \(\left[ \begin{array}{l}x=-1\\x=-\dfrac{1}{2}\end{array} \right.\)