On the X2 power + (5 + 5b) xy-x + 2x + 7 of the polynomial (A-2) of x y, excluding binomial, finding the value of a-2b? Online and other answers, thank you

On the X2 power + (5 + 5b) xy-x + 2x + 7 of the polynomial (A-2) of x y, excluding binomial, finding the value of a-2b? Online and other answers, thank you

(a-2)x^2+(5+b)xy-x+2x+7
The above formula does not contain binomial, that is to say, the coefficients of quadratic terms are all 0,
That is, A-2 = 0 = = > A = 2
5+5b=0 ==> b=-1
Then a-2b = 2-2 × (- 1) = 2 + 2 = 4