若ab=-2,求(2a+2b)²-(2a-2b)²的值
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若ab=-2,求(2a+2b)²-(2a-2b)²的值
若ab=-2,求(2a+2b)²-(2a-2b)²的值
若ab=-2,求(2a+2b)²-(2a-2b)²的值
=(2a+2b+2a-2b)(2a+2b-2a+2b)
=4a×4b
=16ab
=16×(-2)
=-32
若ab=-2,求(2a+2b)²-(2a-2b)²的值
(2a+2b)²-(2a-2b)²
=(2a+2b+2a-2b)(2a+2b-2a+2b)
=4a*4b
=16ab
=-32
原式=4a^2+8ab+4b^2-(4a^2-8ab+4b^2)=16ab=16*(-2)=-32
(2a+2b)² - (2a-2b)² = 4a²+8ab+4b² - (4a²-8ab+4b²) = 16ab = -32