已知a+b=7/4,ab=3/4,求1/2a^3b+1/2ab^3的值

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已知a+b=7/4,ab=3/4,求1/2a^3b+1/2ab^3的值已知a+b=7/4,ab=3/4,求1/2a^3b+1/2ab^3的值已知a+b=7/4,ab=3/4,求1/2a^3b+1/2a

已知a+b=7/4,ab=3/4,求1/2a^3b+1/2ab^3的值
已知a+b=7/4,ab=3/4,求1/2a^3b+1/2ab^3的值

已知a+b=7/4,ab=3/4,求1/2a^3b+1/2ab^3的值
1/2a^3b+1/2ab^3
=1/2ab(a^2+b^2)
=1/2ab[(a+b)^2-2ab]
=1/2×3/4×[(7/4)^2-2×3/4]
=3/8×(49/16-3/2)
=3/8×(49/16-24/16)
=3/8×25/16
=75/128

1/2a^3b+1/2ab^3=1/2ab(a^2+b^2)=1/2ab((a+b)^2-2ab)=75/128

1/2a^3b+1/2ab^3=1/2ab(a^2+b^2)=1/2ab[(a+b)^2-2ab]