proving a given quadratic equation does not have rational roots

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given a,b,c are rational , prove that $(a+b-c)x^2 +(a+c-b)x+(b+c-a)=0$ does not have rational roots. i tried finding discriminant which simplified to $-3b^2+5c^2+5a^2-6ac-2bc-2ba$.now how to prove that it is not a perfect square of a rational number?