(a+b)(a-b)-(a+b)²,其中a=3,b=1/3
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(a+b)(a-b)-(a+b)²,其中a=3,b=1/3
(a+b)(a-b)-(a+b)²,其中a=3,b=1/3
(a+b)(a-b)-(a+b)²,其中a=3,b=1/3
=(a²-b²)-(a²+2ab+b²)
=a²-b²-a²-2ab-b²
= -2ab-2b²
= -2b(a+b)
= -2×(1/3)×(3+1/3)
= -20/9
原式=10/3 * 8/3 - 100/9 =80/9 -100/9 = -20/9