Giải thích các bước giải:
a, x ² - 14x+13 = 0
=> x ² - 13x-x+13 = 0
=>x(x-13)-(x-13)=0
=>(x-1)(x-13)=0
=>\(\left[ \begin{array}{l}x-13=0\\x-1=0\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=13\\x=1\end{array} \right.\)
b, x ² + 8x +7= 0
=> x ² + 7x+x +7= 0
=>x(x+7)+(x+7)=0
=>(x+1)(x+7)=0
=>\(\left[ \begin{array}{l}x+7=0\\x+1=0\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=-7\\x=-1\end{array} \right.\)
c)x ² +10x +16 = 0
=>x ² +8x +2x+16 = 0
=>x(x+8)+2(x+8)=0
=>(x+2)(x+8)=0
=>\(\left[ \begin{array}{l}x+8=0\\x+2=0\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=-8\\x=-2\end{array} \right.\)
d, 4x ² +12x+5 = 0
=> 4x ² +2.2.3x+9-4 = 0
=>$(2x+3)^{2}$-4=0
=>(2x+3-4)(2x+3+4)=0
=>(2x-1)(2x+7)=0
=>\(\left[ \begin{array}{l}2x-1=0\\2x+7=0\end{array} \right.\)
=>\(\left[ \begin{array}{l}2x=1\\2x=-7\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=$\frac{1}{2}$ \\x=$\frac{-7}{2}$ \end{array} \right.\)
e)x ³ +3x ² +3x +1 =0
(x+1)^3=0
=>x+1=0
=>x=-1
