Search for: If a>0 and coefficient of x2, x3, x4 in the expansion of 1+xa6 are in A.P., then a equalsIf a>0 and coefficient of x2, x3, x4 in the expansion of 1+xa6 are in A.P., then a equalsA(4+7)3B(4+3)3C2−3D2+3 Register to Get Free Mock Test and Study Material Grade ---Class 6Class 7Class 8Class 9Class 10Class 11Class 12 Target Exam JEENEETCBSE +91 Preferred time slot for the call ---9 am10 am11 am12 pm1 pm2 pm3 pm4 pm5 pm6 pm7 pm8pm9 pm10pmPlease indicate your interest Live ClassesRecorded ClassesTest SeriesSelf LearningVerify OTP Code (required) I agree to the terms and conditions and privacy policy. Solution:Coefficient of xr in the expansion of (1+x/a)6=6Cr(1/a)r According to given condition 6C2(1/a)2,6C3(1/a)3,6C4(1/a)4are in A.P.∴ 2 6C31a3=6C21a2+6C41a4⇒ 2(20)a=15a2+1⇒ 3a2−8a+3=0⇒ a=(4+7)3 as a>0.Related content Distance Speed Time Formula Refractive Index Formula Mass Formula Electric Current Formula Ohm’s Law Formula Wavelength Formula Electric Power Formula Resistivity Formula Weight Formula Linear Momentum Formula