Question

Tính hợp lí:

(29 - 9).(-9)+(-13-17).21

Answer 1

\(\left(29-9\right).\left(-9\right)+\left(-13-17\right).21\\ =20.\left(-9\right)+\left(-30\right).21\\ =\left(-180\right)+\left(-630\right)\\ =-810\)

Answer 2

= 20.(-9) + (-20) .21

= 20 .(-9 ) + 20 . (-21)

= 20 . (-9-21)

= 20 . (-30 )

=(-60)

Answer 3