Find the range of rational expression y=x2+34x−71x2+2x−7 if x is real
(−∞,5]∪[9,∞)
y=x2+34x−71x2+2x−7⇒ x2(y−1)+x(2y−34)+(71−7y)=0
Given that x is real
⇒b2−4ac≥0⇒(2y−34)2−4(y−1)(71−7y)≥04[y2+289−34y+7y2−78y+71]≥ 0y2−14y+45≥0y(y−9)−5(y−9)≥0(y−5)(y−9)≥0
for y≤5 & y≥ 9y≤ 5 and y ≥ 9Hence y ϵ(−∞,5]∪[9,∞)