Question

Thực hiện phép tính 1 cách hợp lý

a, A = ( 1/3 + 12/67 + 13/41 ) - ( 79/67 - 28/41)

b, B = 3/4×7 + 3/7×10 + 3/10×13 + .....+ 3/73×76

c, C = 5/9 × 7/13 + 9/13 × 5/9 - 5/9 × 3/13

Answer 1

a, A = (\(\dfrac{1}{3}+\dfrac{12}{67}+\dfrac{13}{41}\)) - (\(\dfrac{79}{67}-\dfrac{28}{41}\))

= \(\dfrac{1}{3}+\dfrac{12}{67}+\dfrac{13}{41}-\dfrac{79}{67}+\dfrac{28}{41}\)

= \(\dfrac{1}{3}+\left(\dfrac{12}{67}-\dfrac{79}{67}\right)+\left(\dfrac{13}{41}+\dfrac{28}{41}\right)\)
= \(\dfrac{1}{3}-1+1\)

= \(\dfrac{1}{3}\)

@Mai Tran