问题
解答题
利用乘法公式进行计算: (1)19
(2)(79
|
答案
(1)19
×203 4 1 4
=(20-
)×(20+1 4
)1 4
=202-(
)21 4
=400-1 16
=399
;15 16
(2)(79
)2=(80-4 5
)21 5
=802-2×80×
+(1 5
)21 5
=6400-32+1 25
=6368
.1 25
利用乘法公式进行计算: (1)19
(2)(79
|
(1)19
×203 4 1 4
=(20-
)×(20+1 4
)1 4
=202-(
)21 4
=400-1 16
=399
;15 16
(2)(79
)2=(80-4 5
)21 5
=802-2×80×
+(1 5
)21 5
=6400-32+1 25
=6368
.1 25