Đáp án:
1) 16 - 8x = 0
⇔ 16 = 8x
⇔ x = 2
2) 5x - 3 = 16 - 8x
⇔ 5x + 8x = 16 + 3
⇔ 13x = 19
⇔ $\frac{19}{13}$
3) $\frac{5x - 4}{2}$ = $\frac{16x + 1}{7}$
⇔ $\frac{35x - 28}{14}$ = $\frac{32x + 2}{14}$
⇔ 35x - 28 = 32x + 2
⇔ 35x - 32x = 2 + 28
⇔ 3x = 30
⇔ x = 10
4) -$x^{2}$ -12x + 21 = (3-x)(x+11)
⇔ -$x^{2}$ -12x + 21 = -8x + 33 -$x^{2}$
⇔ -4x = 12
⇔ x = -3
5) Giống câu 3 nhé
6) $\frac{7x - 2}{12}$ + $\frac{2 - x}{4}$ = $\frac{3x + 1}{3}$
⇔ $\frac{7x-2}{12}$ + $\frac{6 - 3x}{12}$ = $\frac{12x + 4}{12}$
⇔ 7x - 2 + 6 - 3x = 12x + 4
⇔ 0 = 8x
⇔ x = 0
7) $\frac{5(x - 2)}{4}$ -3x + $\frac{5x - 3}{6}$ = $\frac{4x - 1}{3}$
⇔ $\frac{13x - 30}{12}$ - $\frac{36x}{12}$ + $\frac{10x - 6}{12}$ = $\frac{16x - 4}{12}$
⇔ 13x - 30 - 36x + 10x - 6= 16x - 4
⇔ -29x = 32
⇔ x = $\frac{-32}{29}$
