Bài 1 : Tìm x a. x – 105 ÷ 21 = 15 b. ( 2x – 1 ) × 5^4 = 3 × 5^5 c. 26 + 5 × 2^x+2 = 106 15/11/2021 Bởi Eloise Bài 1 : Tìm x a. x – 105 ÷ 21 = 15 b. ( 2x – 1 ) × 5^4 = 3 × 5^5 c. 26 + 5 × 2^x+2 = 106
a) $x – 105 : 21 = 15$ $x – 5 = 15$ $x = 15 + 5$ $x = 20$ b) $\text{ (2x – 1) . $5^{4}$ = 3 . $5^{5}$}$ $\text{(2x – 1) . 625 = 3 . 3125}$ $\text{ (2x – 1) . 625 = 9375}$ $\text{2x – 1 = 9375 : 625}$ $\text{2x – 1 = 15}$ $\text{2x = 15 + 1}$ $\text{2x = 16}$ $\text{x = 16 : 2}$ $\text{x = 8}$ c) $\text{26 + 5.$2^{x + 2}$ = 106}$ $\text{5.$2^{x + 2}$ = 106 – 26}$ $\text{5.$2^{x + 2}$ = 80}$ $\text{$2^{x + 2}$ = 80 : 5}$ $\text{$2^{x + 2}$ = 16}$ $\text{$2^{x + 2}$ = $2^{4}$}$ ⇒ $\text{x + 2 = 4}$ $\text{x = 4 – 2}$ $\text{x = 2}$ Vậy $x = 2$ Bình luận
a) $x – 105 : 21 = 15$
$x – 5 = 15$
$x = 15 + 5$
$x = 20$
b) $\text{ (2x – 1) . $5^{4}$ = 3 . $5^{5}$}$
$\text{(2x – 1) . 625 = 3 . 3125}$
$\text{ (2x – 1) . 625 = 9375}$
$\text{2x – 1 = 9375 : 625}$
$\text{2x – 1 = 15}$
$\text{2x = 15 + 1}$
$\text{2x = 16}$
$\text{x = 16 : 2}$
$\text{x = 8}$
c) $\text{26 + 5.$2^{x + 2}$ = 106}$
$\text{5.$2^{x + 2}$ = 106 – 26}$
$\text{5.$2^{x + 2}$ = 80}$
$\text{$2^{x + 2}$ = 80 : 5}$
$\text{$2^{x + 2}$ = 16}$
$\text{$2^{x + 2}$ = $2^{4}$}$
⇒ $\text{x + 2 = 4}$
$\text{x = 4 – 2}$
$\text{x = 2}$
Vậy $x = 2$