Ta có:
\(\displaystyle A = \left[ {0,8.7 + {{\left( {0,8} \right)}^2}} \right]\left( {1,25.7 - {4 \over 5}.1,25} \right) + 31,64\)
\(A = \left[ {0,8.7 + {{\left( {0,8} \right)}^2}} \right]\left( {1,25.7 - 0,8.1,25} \right) + 31,64\)
\(A = 0,8 . (7+0,8) . 1,25.(7 - 0,8) + 31,64\)
\(A = 0,8 . 7,8 . 1,25 . 6,2 + 31,64\)
\(A = (0,8 . 1,25) . (7,8 . 6,2) + 31,64\)
\( A = 1 . 48,36 + 31,64 = 80\)
\( A = 48,36 + 31,64 = 80\)
\(\begin{array}{l}B = \dfrac{{\left( {1,09 - 0,29} \right).\dfrac{5}{4}}}{{\left( {18,9 - 16,65} \right).\dfrac{8}{9}}}\\B = \dfrac{{0,8.1,25}}{{2,25.\dfrac{8}{9}}} = \dfrac{{0,8.1,25}}{{\dfrac{9}{4}.\dfrac{8}{9}}} = \dfrac{1}{2}\end{array}\)
Ta có \(\displaystyle {\rm{A}}:B = 80:{1 \over 2} = 80.{2 \over 1} = 160\)
Vậy A gấp B là \(160\) lần.
