Bài 13Rút gọn các biểu thức sau:
b) (25.9-25.17)/((-8).80-8.10)
(48.12-48.15)/((-3).270-3.30) ;
(1998.1990+3978)/(1992.1991-3984) ;
(2^5.7+2^5)/(2^5.5^2-2^5.3) ;
Bài 13Rút gọn các biểu thức sau: b) (25.9-25.17)/((-8).80-8.10) (48.12-48.15)/((-3).270-3.30) ; (1998.1990+3978)/(1992.1991-3984) ; (2^5.7+2^5)/(2
By Alexandra
$\dfrac{25.9 – 25.7}{(-8.80 – 8.10)}$
`= `$\dfrac{25.(9 – 17)}{8.(-80) – 8.10}$
`= `$\dfrac{25.8}{8.[(-80) – 10]}$
`= `$\dfrac{25.8}{8.(-90)}$
`= `$\dfrac{25}{-90}$
`= `$\dfrac{-5}{18}$
$\dfrac{48.12 – 48.15}{(-3).270 – 3.30}$
`= `$\dfrac{48.(12 – 15)}{(-3).(270 + 30)}$
`= `$\dfrac{48.(-3)}{(-3).300}$
`= `$\dfrac{48}{300}$
`= `$\dfrac{4}{25}$
$\dfrac{1989.1990 + 3978}{1992.1991 – 3984}$
`= `$\dfrac{1989.1990 + 1989.2}{1992.1991 – 1992.2}$
`= `$\dfrac{1989.(1990 + 2)}{1992.(1991 – 2)}$
`= `$\dfrac{1989.1992}{1992.1989}$
`= 1.`
$\dfrac{2^5.7 + 2^5}{2^5.5^2 – 2^5.3}$
`= `$\dfrac{2^5.(7 + 1)}{2^5.(25 – 3)}$
`= `$\dfrac{8}{22}$
`= `$\dfrac{4}{11}$