Thực hiện phép tính ( hợp lí nếu có thể): a, 25.(-1/2)mũ 2 + 1/5-2.(-1/2)mũ 2 – 1/2 03/12/2021 Bởi Alexandra Thực hiện phép tính ( hợp lí nếu có thể): a, 25.(-1/2)mũ 2 + 1/5-2.(-1/2)mũ 2 – 1/2
Giải thích các bước giải: Ta có:$A=25\cdot \left(-\dfrac12\right)^2+\dfrac15-2\cdot \left(-\dfrac12\right)^2-\dfrac12$ $\to A=25\cdot \left(\dfrac12\right)^2+\dfrac15-2\cdot \left(\dfrac12\right)^2-\dfrac12$ $\to A=25\cdot \dfrac14+\dfrac15-2\cdot \dfrac14-\dfrac12$ $\to A=25\cdot \dfrac14+\dfrac15- \dfrac12-\dfrac12$ $\to A=25\cdot \dfrac14+\dfrac15-\left( \dfrac12+\dfrac12\right)$ $\to A=\dfrac{25}4+\dfrac15-1$ $\to A=\dfrac{125}{20}+\dfrac4{20}-\dfrac{20}{20}$ $\to A=\dfrac{125+4-20}{20}$ $\to A=\dfrac{109}{20}$ Bình luận
`\text{~~Holi~~}` `a. 25.(-1/2)^2+1/5-2.(-1/2)^2-1/2` `= 23.(-1/2)^2+1/5-1/2` `= 23.1/4+1/5-1/2` `= (23)/4+1/5-1/2` `= (109)/(20)` Bình luận
Giải thích các bước giải:
Ta có:
$A=25\cdot \left(-\dfrac12\right)^2+\dfrac15-2\cdot \left(-\dfrac12\right)^2-\dfrac12$
$\to A=25\cdot \left(\dfrac12\right)^2+\dfrac15-2\cdot \left(\dfrac12\right)^2-\dfrac12$
$\to A=25\cdot \dfrac14+\dfrac15-2\cdot \dfrac14-\dfrac12$
$\to A=25\cdot \dfrac14+\dfrac15- \dfrac12-\dfrac12$
$\to A=25\cdot \dfrac14+\dfrac15-\left( \dfrac12+\dfrac12\right)$
$\to A=\dfrac{25}4+\dfrac15-1$
$\to A=\dfrac{125}{20}+\dfrac4{20}-\dfrac{20}{20}$
$\to A=\dfrac{125+4-20}{20}$
$\to A=\dfrac{109}{20}$
`\text{~~Holi~~}`
`a. 25.(-1/2)^2+1/5-2.(-1/2)^2-1/2`
`= 23.(-1/2)^2+1/5-1/2`
`= 23.1/4+1/5-1/2`
`= (23)/4+1/5-1/2`
`= (109)/(20)`