Tìm x thuộc N biết a, (x trừ 3) chia 2 = 5 mũ 14 chia 5 mũ 12

* Hướng dẫn giải

a, $\left(x-3\right):2=5^{14}:5^{12}$

=> $\left(x-3\right):2=5^2$

=> $\left(x-3\right):2=25$

=> x – 3 = 25

=> x = 53

b, $30:\left(x-7\right)={15}^{19}:{15}^{18}$

=> $30:\left(x-7\right)=15$

=> x – 7 = 2

=> x = 9

c, $x^{70}=x$

=> $x^{70}-x=0$

=> $x(x^{69}-1)=0$

=> 

d, ${\left(2x+1\right)}^3=9.81$

=> ${\left(2x+1\right)}^3=9^3$

=> 2x + 1 = 9

=> x = 4

e, $5^x+5^{x+2}=650$

=> $5^x\left(1+5^2\right)=650$

=> $5^x.26=650$

=> $5^x=25$

=> x = 2

f, ${\left(4x-1\right)}^2=25.9$

=> ${\left(4x-1\right)}^2=5^2.3^2$

=> ${\left(4x-1\right)}^2={15}^2$

=> 4x – 1 = 15

=> x = 4