先化简再求值 (2a-3b)^2-(2a+3b)(2a-3b)+(2a+3b)^2其中a+-2,b=1/3
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先化简再求值 (2a-3b)^2-(2a+3b)(2a-3b)+(2a+3b)^2其中a+-2,b=1/3
先化简再求值 (2a-3b)^2-(2a+3b)(2a-3b)+(2a+3b)^2其中a+-2,b=1/3
先化简再求值 (2a-3b)^2-(2a+3b)(2a-3b)+(2a+3b)^2其中a+-2,b=1/3
(2a-3b)^2-(2a+3b)(2a-3b)+(2a+3b)^2
= (2a-3b)^2-2(2a+3b)(2a-3b)+(2a+3b)^2+(2a+3b)(2a-3b)
=(2a-3b-2a-3b)^2+(2a+3b)(2a-3b)
=36b^2+4a^2-9b^2
=27b^2+4a^2
=27*1/9+4*4
=3+16
=19
(2a-3b)^2-(2a+3b)(2a-3b)+(2a+3b)^2
=[(2a-3b)-(2a+3b)]^2+(2a+3b)(2a-3b)
=36b^2+4a^2-9b^2
=27b^2+4a^2
将a=-2,b=1/3代入,
原式=27*(1/3)^2+4*(-2)^2=3+16=19