The roots of x2+a2=8x+6a  are real, then a∈

Δ≥0⇒b2−4ac≥0             ⇒64−4(a2−6a)≥0            ⇒ a2−6a−16≤0            ⇒(a+2)(a−8)≤0            ⇒a∈[−2,8]