a, -7.3x-5+2.7x-14=28
=> -21x - 5 + 14x - 14 = 28
=> -21x + 14x = 28 + 14 + 5
=> -7x = 47
=> x = $\frac{-47}{7}$
Vậy x = $\frac{-47}{7}$
b, 10|4x-8|+20=180
=> 10.|4x-8| = 160
=> |4x-8| = 16
=> \(\left[ \begin{array}{l}4x-8=16\\4x-8=-16\end{array} \right.\)
=> \(\left[ \begin{array}{l}x=6\\x=-2\end{array} \right.\)
Vậy x = 6 hoặc x = -2
c, $x^{2}$ + x = 0
=> x.(x+1) = 0
=> \(\left[ \begin{array}{l}x=0\\x+1=0\end{array} \right.\)
=> \(\left[ \begin{array}{l}x=0\\x=-1\end{array} \right.\)
Vậy x = 0 hoặc x = -1
