Question

[Hưng phắc]

Bài 1 tính giá trị các bt sau

b) B=m(m-n+1)-n(n+1-m) vs m= -2/3 n = - 1/3

Answer 1

[hưng phúc]

B = m(m - n + 1) - n(n + 1 - m) 

B = m² - mn + m - n² - n + mn

B = m² + m - mn + mn - n² - n

B = m² + m - n² - n

Thay \(m=-\dfrac{2}{3};n=-\dfrac{1}{3}\), ta được:

B =\(\left(-\dfrac{2}{3}\right)^2+\left(-\dfrac{2}{3}\right)-\left(-\dfrac{1}{3}\right)^2-\left(-\dfrac{1}{3}\right)\)

B = \(\dfrac{4}{9}-\dfrac{2}{3}-\dfrac{1}{9}+\dfrac{1}{3}\)

B = \(\dfrac{3}{9}-\dfrac{1}{3}\)

B = \(\dfrac{1}{3}-\dfrac{1}{3}=0\)

Answer 2

[Hưng phắc]

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