如何简便计算19.98的平方
如何简便计算19.98的平方 -
19.98²=(20-0.02)#178;=20²-2x20x0.02+0.02²=400+0.8+0.0004=400.8004
19.98的平方-0.02的平方=(19.98+0.02)(19.98-0.02)=20*19.96 =399.2
19.98²=(20-0.02)#178;=20²-2x20x0.02+0.02²=400+0.8+0.0004=400.8004
19.98的平方-0.02的平方=(19.98+0.02)(19.98-0.02)=20*19.96 =399.2
(1)19.98 2 -0.02 2 =(19.98+0.02)×(19.98-0.02)20×19.96=399.2;(2)126×52 2 -48 2 ×126=126×(52 2 -48 2 )126×(52+48)×(52-48)126×100×4=50400.
=19.98×(37-19+82)19.98×100 =1998
199.9×19.98-199.8×19.97简便计算 -
199.9×19.98-199.8×19.97 =199.9×19.98-19.98×10×19.97 =199.9×19.98-19.98×199.7 =19.98×(199.9-199.7)19.98×0.2 =(20-0.02)×0.2 =4-0.04 =3.96
19.98×37-199.8×1.9+1.998×20 =19.98×37-19.98×19+19.98×2 =19.98*(37-19+2)=19.98*(20)=399.6
19.9+19.98+19.997+19.9996怎么用简便计算 -
=(20-0.1)(20-0.02)(20-0.003)(20-0.0004)=20*4-0.1234 =80-0.1234 =79.8766
(1)0.83×6.89-1.89×0.83=0.83×(6.89-1.89)0.83×5=4.15;(2)19.98-7.88-2.12=19.98-(7.88+2.12)19.98-10=9.98.
简便计算1998+199.8+19.98+1.998等於多少?要简便的 -
2000+200+20+2-2-0.2-0.02-0.002 =2222-2-0.2-0.02-0.002 =2219.778 把1998看作是2000-2 把199.8看作200-0.2 把19.98看作20-0.02 把1.998看作是2-0.002 就行了,
199.7×19.98-199.8×19.96 =199.7×19.98-19.98×199.6 =(199.7-199.6)×19.98 =0.1×19.98 =1.998