Can you use Calculus and does a=A?
substituting: -1, 0, 1
a(-1) + b(-1) + c = c - a - b
a(-1) + b( 0) + c = c - a
a(-1) + b(+1) + c = c - a + b
a(0) + b(-1) + c = c - b
a(0) + b( 0) + c = c
a(0) + b(+1) + c = c + b
a(+1) + b(-1) + c = c + a - b
a(+1) + b( 0) + c = c + a
a(+1) + b(+1) + c = c + a + b
Those are the maximum & minimum values possible.
IF you know the sign value of a,b,c then you can determine exactly which case applies.
Without knowing the positive/negative magnitudes of a,b,c you cannot give a specific answer.
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