અહી \(a\) અને \(\mathrm{b}\) અનુક્રમે વિધેય \(f(x)=2 x^{3}-3 x^{2}-12 x \) ની સ્થાનીય મહતમ અને સ્થાનીય ન્યૂનતમ દર્શાવે છે . જો \(A\) એ \(\mathrm{y}=\mathrm{f}(\mathrm{x})\), \(\mathrm{x}\)-અક્ષ અને રેખાઓ \(x=a\) અને \(x=b\) દ્વારા આવૃત પ્રદેશનું ક્ષેત્રફળ હોય તો \(4 A\) ની કિમંત મેળવો.

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.