Question

Bài 2(2,5 điểm): Tìm số tự nhiên x, biết

a)2x+34=56                                                                                                           

     b)87–(x – 654):3=  21                                                                                             

     c)7⁶⁵:7^X  =  7⁴³.7²¹

Answer 1

\(a,2x+34=56\\ \Rightarrow2x=56-34\\ \Rightarrow x=22:2\\ \Rightarrow x=11\\ b,87-\left(x-654\right):3=21\\ \Rightarrow\left(x-654\right):3=87-21\\ \Rightarrow x-654=66:3\\ \Rightarrow x=22+654\\ \Rightarrow x=676\\ c,7^{65}:7^x=7^{43}.7^{21}\\ \Rightarrow7^{65-x}=7^{43+21}\\ \Rightarrow65-x=64\\ \Rightarrow x=65-64\\ \Rightarrow x=1\)