Q.
If x is real, then the value of the expression x2+2x−7x2+34x−71 does not exist between -
122
154
Complex Numbers and Quadratic Equations
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Solution:
x2+2x−7x2+34x−71=y x2(1−y)+x(34−2y)−71+7y=0 x∈RD≥0 4(17−y)2−(7y−71)(1−y)≥0 (17−y)2−[7y−7y2−71+71y]≥0 289+y2−34y−7y+7y2+71−71y≥0 8y2−112y+360>0 y2−14y+45≥0 (y−5)(y−9)≥0 y does not lie b/w 5&9