If the quadratic functions F1 (x) = a1x ^ 2 + b1x + C1 and F2 (x) = a2x ^ 2 + b2x + C2 such that F2 (x) + F1 (x) is listed as an increasing function in (- ∞, + ∞), the condition is

If the quadratic functions F1 (x) = a1x ^ 2 + b1x + C1 and F2 (x) = a2x ^ 2 + b2x + C2 such that F2 (x) + F1 (x) is listed as an increasing function in (- ∞, + ∞), the condition is

f2(x)+f1(x)
=(a1+a2)x²+(b1+b2)x+(c1+c2)
If a1 + A2 ≠ 0, then the function is quadratic and not increasing in (- ∞, + ∞)
therefore
a1+a2=0
b1+b2>0