Đề bài

Tìm x, biết: a)\(0,{7^2}.x = 0,{49^3}\); b)\(x:{\left( { - 0,5} \right)^3} = {\left( { - 0,5} \right)^2}\)

Lời giải chi tiết

a)\(\begin{array}{l}0,{7^2}.x = 0,{49^3}\\ \Rightarrow 0,{7^2}.x = {\left[ {{{\left( {0,7} \right)}^2}} \right]^3}\\ \Rightarrow 0,{7^2}.x = 0,{7^6}\\ \Rightarrow x = (0,7)^6:(0,7)^2\\ \Rightarrow x = (0,7)^{6 - 2}\\ \Rightarrow x = (0,7)^4\end{array}\)Vậy \(x = (0,7)^4\)b)\(\begin{array}{l}x:{\left( { - 0,5} \right)^3} = {\left( { - 0,5} \right)^2}\\ \Rightarrow x = {\left( { - 0,5} \right)^2}.{\left( { - 0,5} \right)^3}\\ \Rightarrow x = {\left( { - 0,5} \right)^{2 + 3}}\\ \Rightarrow x = {\left( { - 0,5} \right)^5}\end{array}\)Vậy \(x = {\left( { - 0,5} \right)^5}\)