先化简再求值(m²+3m)(m-3)-m(m-2)²,其中m=-2
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先化简再求值(m²+3m)(m-3)-m(m-2)²,其中m=-2
先化简再求值(m²+3m)(m-3)-m(m-2)²,其中m=-2
先化简再求值(m²+3m)(m-3)-m(m-2)²,其中m=-2
原式 = m(m + 3)(m - 3)- m(m - 2)²
= m(m ² - 9)- m(m ² - 4 m + 4)
= m(m ² - 9 - m ² + 4 m - 4)
= m(4 m - 13)
= 4 m ² - 13 m
当 m = - 2 时,原式 = 4 × (- 2)² - 13 × (- 2)
= 4 × 4 + 26
= 16 + 26
= 42
m(m+3)(m-3)-m(m-2)
m(m^2-9)-m(m-2)
m(m^2-9-m+2)
m(m^2-m-7)
将m=-2带入
∴-2(4+2-7)=2
(m²+3m)(m-3)-m(m-2)²
=m[(m+3)(m-3)-(m-2)²]
=m(m²-9-m²+4m-4)
=m(4m-13)
=4m²-13m
=16+26
=42
(m²+3m)(m-3)-m(m-2)²=m(m+3)(m-3)-m(m-2)²=m[ (m+3)(m-3)-(m-2)²]=m(m²-9-m²-4+4m)=m(4m-13)=42