Bài 51 trang 17 SBT toán 7 tập 1

Đề bài

Tính:

a) \(\displaystyle {{{{120}^3}} \over {{{40}^3}}}\)                   b) \(\displaystyle {{{{390}^4}} \over {{{130}^4}}}\)

c) \(\displaystyle {{{3^2}} \over {{{\left( {0,375} \right)}^2}}}\)

a) \(\displaystyle {{{{120}^3}} \over {{{40}^3}}} = {\left( {{{120} \over {40}}} \right)^3} = {3^3} = 27\) 

b) \(\displaystyle {{{{390}^4}} \over {{{130}^4}}} = {\left( {{{390} \over {130}}} \right)^4} = {3^4} = 81\)

c) \(\displaystyle {{{3^2}} \over {{{\left( {0,375} \right)}^2}}} = {\left( {{3 \over {0,375}}} \right)^2} = {\left( {\frac{3}{{\dfrac{3}{8}}}} \right)^2}\)

\(\displaystyle ={\left( {3.\frac{8}{3}} \right)^2}= {8^2} = 64\).