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.
用乘法公式计算:
(1)59.8×60.2;
(2)(x+5)2-(x-3)2
(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.