Bài này nữa ạ. Em cảm ơn nhiều ạ.

`1.`

`a.`

`A = 5*sqrt(5) + 3*sqrt(5) - 9*sqrt(5) = (5+3-9)*sqrt(5) = -sqrt(5) `

`b.`

`B = 5*sqrt(2) - 8*sqrt(2) + 9*sqrt(2) - 3*sqrt(2) = (5-8+9-3)*sqrt(2) = 3*sqrt(2)`

`c.`

`C = 3*sqrt(7) - 6*sqrt(7) - 7*sqrt(7) + 5*sqrt(7) = (3-6-7+5)*sqrt(7) = -5*sqrt(7)`

`2.`

`a.`

` A = 10*sqrt(2) - 4*sqrt(2) + 6*sqrt(2) = (10-4+6)*sqrt(2) = 12*sqrt(2)`

`b.`

`B = 8*sqrt(5) - 15*sqrt(5) + 15*sqrt(5) - 3*sqrt(5) = (8-15+15-3)*sqrt(5) = 5*sqrt(5)`

`c.`

`C = (3*sqrt(5) - 3*sqrt(2))*(4*sqrt(2) - 10*sqrt(5)) = 6*(7*sqrt(10) - 29) = 42*sqrt(10) - 174`

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