Q.

If the domain of the function f(x)=log(0.6)(|2x–5x2–4|) is (–∞,a]∪{b}∪[c,d)∪(e,∞), then the value of a + b + c + d + e is ________.          [2026]


Ans.

(4)

We have, f(x)=log(0.6)(|2x–5x2–4|)

log0.6|2x–5x2–4|≥0

⇒ |2x–5x2–4|≤1

⇒ |2x–5|≤|x2–4|; x≠52, 2, –2

Also, |2x–5|≤|x2–4|

⇒ (2x–5)2≤(x2–4)2

⇒ (x2–4+2x–5)(x2–4–2x+5)≥0

⇒ (x2+2x–9)(x2–2x+1)≥0

⇒ (x2+2x–9)(x–1)2≥0

Since, (x–1)2≥0

⇒ x2+2x–9≥0

⇒ x∈(–∞,–1–10]∪[1}∪(–1+10,∞)

exclude x = 2, 52          (∵ –2 is already excluded)

Hence, x∈(–∞,–1–10]∪[1}∪(–1+10,5/2)∪(5/2,∞)

         x∈(–∞,a]∪[b}∪[c,d)∪(e,∞)          (Given)

∴ a=–1–10, b=1, c=–1+10, d=5/2, e=5/2

∴ a + b + c + d + c = 4.