展开 Dr(pir^2+ar)

解答

展开

Dr (π r^{2} + a r)

π D r^{3} + D a r^{2}

求解步骤

Dr (π r^{2} + a r)

使用分配律:

a (b + c) = ab + a c

a = Dr, b = π r^{2}, c = a r

= Dr π r^{2} + Dr a r

= π D r^{2} r + D a rr

化简

π D r^{2} r + D a rr : π D r^{3} + D a r^{2}

= π D r^{3} + D a r^{2}

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