## a) 142 – 11 mũ 2x+1 : 11 = 21 b) 4 mũ 2x+1 – 14.4 = 8 c) 3 mũ x – 1 + 2.3 mũ x = 7 d) 3 mũ x + 4 mũ x = 7

Question

a) 142 – 11 mũ 2x+1 : 11 = 21 b) 4 mũ 2x+1 – 14.4 = 8 c) 3 mũ x – 1 + 2.3 mũ x = 7
d) 3 mũ x + 4 mũ x = 7

in progress 0
4 tuần 2021-07-11T00:52:49+00:00 1 Answers 3 views 0

1. Giải thích các bước giải:

$a)142-11^{2x+1}:11=21$

$⇔142-11^{2x+1}:11^1=21$

$⇔11^{2x+1-1}=142-21$

$⇔11^{2x}=121$

$⇔11^{2x}=11^2$

$⇔2x=2$

$⇔x=1$

$\text{Vậy$x=1$}$

$b) 4^{2x+1}-14.4=8$

$⇔4^{2x+1}-56=8$

$⇔4^{2x+1}=64$

$⇔4^{2x+1}=4^4$

$⇔2x+1=4$

$⇔2x=3$

$⇔x=\dfrac{3}{2}$

$\text{Vậy$x=\dfrac{3}{2}$}$

$c)3^x-1+2.3^x=7$

$⇔3×3^x-1=7$

$⇔3^{x+1}-1=7$

$⇔3^{x+1}=8$

$⇔3^{x+1}≈3^{1,9}$

$⇔x+1≈1,9$

$⇔x≈0,9$

$\text{Vậy$x≈0,9$}$

$d)3^x+4^x=7$

$⇔3^x+4^x=3+4$

$⇒x=1$

$\text{Vậy$x=1$}$

Học tốt!!!