Question

Bài 14 : Tính :

a.  25 mũ 3  :  5 mũ 2

b.  ( 3/7 ) mũ 21  :  ( 9/49 ) mũ 6

c.  3 - ( -6/7 ) mũ 0  +  ( 1/2 ) mũ 2  :  2

 

Answer 1

\(25^3\div5^2=\left(5^2\right)^3\div5^2=5^6\div5^2=5^4=625\)

\(\left(\frac{3}{7}\right)^{21}\div\left(\frac{9}{49}\right)^6=\left(\frac{3}{7}\right)^{21}\div\left[\left(\frac{3}{7}\right)^2\right]^6=\left(\frac{3}{7}\right)^{21}\div\left(\frac{3}{7}\right)^{12}=\left(\frac{3}{7}\right)^9\)

\(3-\left(-\frac{6}{7}\right)^0+\left(\frac{1}{2}\right)^2\div2=3-1+\frac{1}{4}\times\frac{1}{2}=2+\frac{1}{8}=\frac{17}{8}\)