问题 解答题

用乘法公式计算:

(1)59.8×60.2;

(2)(x+5)2-(x-3)2

答案

(1)59.8×60.2,

=(60-0.2)(60+0.2),

=602-0.22

=3600-0.04,

=3599.96;

(2)(x+5)2-(x-3)2

=[(x+5)+(x-3)][(x+5)-(x-3)],

=(x+5+x-3)(x+5-x+3),

=16x+16.

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