Toán Lớp 7: 25*(-1 /5)^3 +1 /5 -2*(1 /2)^2 -√1/4
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Toán Lớp 7: 25*(-1 /5)^3 +1 /5 -2*(1 /2)^2 -√1/4
Comments ( 2 )
$25\left(-\dfrac{1}{5}\right)^3+\dfrac{1}{5}-2\left(\dfrac{1}{2}\right)^2-\dfrac{\sqrt{1}}{4}$
$=25\left(-\dfrac{1}{5}\right)^3+\dfrac{1}{5}-2\left(\dfrac{1}{2}\right)^2-\dfrac{1}{4}$
$=-2\left(\dfrac{1}{2}\right)^2+\dfrac{1}{5}-\dfrac{1}{4}+25\left(-\dfrac{1}{5}\right)^3$
$=-\dfrac{1}{2}+\dfrac{1}{5}-\dfrac{1}{4}-\dfrac{1}{5}$
$=-\dfrac{1}{2}-\dfrac{1}{4}$ $=-\dfrac{2}{4}-\dfrac{1}{4}$ $=\dfrac{-2-1}{4}$ $=\dfrac{-3}{4}$
$=-\dfrac{3}{4}$
25 . (-1 /5)^3 +1 /5 -2 . (1 /2)^2 -sqrt{1/4}
= 25 . (1/125) + 1/5 – 2 . (1/4) – 1/2
= 1/5 + 1/5 – 1/2 – 1/2
= 2/5 – 1/2 – 1/2
= 4/10 – 5/10 – 5/10
= (-1/10) – 5/10
= -6/10
= -3/5