Given a, b is a rational number, try to state that a+b-2a-4b+8 is a positive number Let a, b be rational numbers. Let a+b-2a-4b+8 be positive

A+b-2a-4b+8=(a-1)^2+(b-2)^2+3 Because (a-1)^2>=0,(b-2)^2>=0, then (a-1)^2+(b-2)^2+3>0 is a positive number Here, a, b rational numbers, mainly to show a-1, b-2 is a real number, their square >=0

Given that a and b are rational numbers, try to show that the value of a2+b2-2a-4b+8 is positive

Original formula =(a-1)^2+(b-2)^2+3
Because (a-1)^2 and (b-2)^2 are both ≥0
So it's a positive number.

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