要求简便计算.虽然多,但是请您尽量帮帮我,

1个回答

  • 郭敦顒回答:

    ①4.7×4.3=(5-0 .3)(4+0 .3)=20+0 .3-0 .09=20 .21

    ②7.4×3.4=(7+0.4)(3+0 .4)=21+4+0 .16=25 .15

    ③9.3×10.7=(10-0 .7)(10+0 .7)=10 ²-0 .7 ²=99 .51

    ⑩1.94×1.95-1.91×1.98

    =1.94×1.95+0.06×1.95-1.91×1.98-0.09×1.98-0.06×1.95+0.09×198

    =2×1.95-2×1.98-0.117+0.1782=2(1.95-1.98)+0.0612

    =-0.06+0.0612=0.0012

    2、已知a²=11111111115555555556,求a

    共20位,10节,用手工开方得,a=3333333334 (10位数)