Find the smallest value of (−8p7) for which |x2−5x+7−p|=6+|x2−5x+1−p| for all xϵ[−1,3]. ___
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Solution
We must have (x2−5x+1−p)≥0∀xϵ[−1,3]⇒(x2−5x+1−p)≥0∀xϵ[−1,3]upwardparabolawithvertex(x=52,y=−p−214)∴−p−214≥0⇒p+214≤0⇒p≤−214∴pϵ(−∞,214) Smallest value of (−8p7)=−8p7=−87×−214=6