405 x 4 + 405 x 5+ 405 = 405 x (4+5+1) = 405 x 10 = 4050
K nha mk làm nhanh nhất
405 x4 +405 x 5+405
405 x 4 + 405 x 5 +405 x1
=405 x (4 +5+1)
=405 x 10
=4050
405 x 4 + 405 x 5 + 405
= 405 x 4 + 405 x 5 + 405 x 1
= 405 x ( 4 + 5 + 1 )
= 405 x 10
= 4050
405 x 4 + 405 x 5 + 405
=(405x4) + (405x5) + 405
= 1620 + 2025 + 405
= 3645 + 405
= 4050.
405x4+405x5+405=1620+2025+405=3645+405=4050
tík mình nha!!
