tìm x biết
a , 3 1/3x + 16 3/4 = -13,25
b , [ 2 4/5x – 50 ] : 2/3 = 51
c | 2x – 1 | = ( -4 )^2
d , x + 2/5 = -11/15
tìm x biết
a , 3 1/3x + 16 3/4 = -13,25
b , [ 2 4/5x – 50 ] : 2/3 = 51
c | 2x – 1 | = ( -4 )^2
d , x + 2/5 = -11/15
Đáp án:
a) x = $\frac{21}{20}$
b) x = 60
c) x ∈ { $\frac{17}{2}$ : $\frac{-15}{2}$ }
d) x = $\frac{-17}{15}$
Giải thích các bước giải:
a) 3 $\frac{1}{3}$x + 16 $\frac{3}{4}$ = -13,25
$\frac{10}{3}$x + $\frac{67}{4}$ = $\frac{53}{4}$
$\frac{10}{3}$x = $\frac{53}{4}$ – $\frac{67}{4}$
$\frac{10}{3}$x = $\frac{14}{4}$
x = $\frac{14}{4}$ : $\frac{10}{3}$
x = $\frac{42}{40}$
x = $\frac{21}{20}$
b) [ 2 $\frac{4}{5}$x – 50 ] : $\frac{2}{3}$ = 51
$\frac{7}{5}$x – 50 = 51 . $\frac{2}{3}$
$\frac{7}{5}$x – 50 = 34
$\frac{7}{5}$x = 34 + 50
$\frac{7}{5}$x = 84
x = 84 : $\frac{7}{5}$
x = 60
c) | 2x – 1 | = (-4)²
| 2x – 1 | = 16
th1 : 2x – 1 = 16
2x = 16 + 1
2x = 17
x = 17 : 2
x = $\frac{17}{2}$
th2 : 2x -1 = -16
2x = -16 + 1
2x = -15
x = -15 : 2
x = $\frac{-15}{2}$
d) x + $\frac{2}{5}$ = $\frac{-11}{15}$
x = $\frac{-11}{15}$ – $\frac{6}{15}$
x = $\frac{-17}{15}$