Toán Lớp 6: Bài 3. Cho x > y . Tính A, biết: A = -(x + y – z) + (-x + y – z) – (-x – y)
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Toán Lớp 6: Bài 3. Cho x > y . Tính A, biết: A = -(x + y – z) + (-x + y – z) – (-x – y)
Comments ( 2 )
$\textit{Ta có: A = -(x + y – z) + (-x + y – z) – (-x – y)}$
$\textit{ = -x – y + z – x + y – z + x + y}$
$\textit{ = (-x – x + x) + (-y + y + y) + (z – z)}$
$\textit{ = -x – y}$
$\textit{ = y – x}$
$\textit{Mà x > y ⇒ y – x < 0}$
$\textit{⇒ |y – x| = -(y – x) = x – y}$
$\textit{Vậy |A| = |y – x| = x – y}$