Giải câu 2 trang 27 sách phát triển năng lực toán 7 tập 1

Giải câu 2 trang 27 sách phát triển năng lực toán 7 tập 1.

a. $\frac{- 1}{4} - \frac{3}{4} : x = - \frac{11}{36}$

$\Leftrightarrow \frac{- 1}{4} + \frac{11}{36} = \frac{3}{4} : x$

$\Leftrightarrow \frac{1}{18} = \frac{3}{4} : x$

$\Leftrightarrow x = \frac{3}{4} : \frac{1}{18}$

$\Leftrightarrow x = \frac{3}{4} .18$

$\Leftrightarrow x = \frac{27}{2}$

b. $(x - \frac{1}{2}) : \frac{1}{3} + \frac{5}{7} = 9 \frac{5}{7}$

$\Leftrightarrow 3. (x - \frac{1}{2}) = 9 \frac{5}{7} - \frac{5}{7}$

$\Leftrightarrow 3. (x - \frac{1}{2}) = 9$

$\Leftrightarrow x - \frac{1}{2} = 3$

$\Leftrightarrow x = 3 + \frac{1}{2}$

$\Leftrightarrow x = \frac{7}{2}$

c. $- \frac{22}{15} x + \frac{1}{3} = | - \frac{2}{3} + \frac{1}{5} |$

$\Leftrightarrow - \frac{22}{15} x + \frac{1}{3} = | - \frac{7}{15} |$

$\Leftrightarrow - \frac{22}{15} x = \frac{7}{15} - \frac{1}{3}$

$\Leftrightarrow - \frac{22}{15} x = \frac{2}{15}$

$\Leftrightarrow x = \frac{2}{15} : \frac{- 22}{15}$

$\Leftrightarrow x = \frac{2}{15} . \frac{- 15}{22}$

$\Leftrightarrow x = \frac{- 1}{11}$

d. $(5 x - 1) (2 x - \frac{1}{3})$ = 0

$\Leftrightarrow 5 x - 1 = 0$ hoặc $2 x - \frac{1}{3} = 0$

$\Leftrightarrow x = \frac{1}{5}$ hoặc $x = \frac{1}{6}$

e. |3x-2| = 4

$\Leftrightarrow$ 3x-2 = 4 hoặc 3x-2 = -4

$\Leftrightarrow$ x=2 hoặc $x = \frac{- 2}{3}$

f. |3x-2| - 3x = -2

$\Leftrightarrow | 3 x - 2 | = 3 x - 2$

$\Leftrightarrow 3 x - 2 \geq 0$

$\Leftrightarrow x \geq \frac{2}{3}$

g. |3x-2| - 2 = -3x

$\Leftrightarrow | 3 x - 2 | = - (3 x - 2)$

$\Leftrightarrow 3 x - 2 \leq 0$

$\Leftrightarrow x \leq \frac{2}{3}$

h. |5x-3| = |7-x|

$\Leftrightarrow$ 5x-3 = 7-x hoặc 5x-3 = -(7-x)

$\Leftrightarrow 6 x = 10$ hoặc 4x = -4

$\Leftrightarrow x = \frac{5}{3}$ hoặc x = -1