The positive value of λ for which the co-efficient of x 2 in the expansion x 2 x + λ x 2 10 is 720 , is

Question

The positive value of &#955; for which the co-efficient of x 2 in the expansion x 2 x + &#955; x 2 10 is 720 , is

Aicharya · Accepted Answer

Coefficient of x 2 in x 2 x + &#955; x 2 10 = coefficient of x 0 in x + &#955; x 2 10 A general term in the expansion x + &#955; x 2 10 is 10 C r x 10 - r &#955; x 2 r = 10 C r &#955; r x 5 - 5 r 2 &#8658; coefficient of x 0 = &#8201; 10 C 2 &#955; 2 (for r = 2 ) = 45 &#955; 2 Now 45 &#955; 2 = 720 &#8658; &#955; = &#177; 4

The positive value of λ for which the co-efficient of x 2 in the expansion x 2 x + λ x 2 10 is 720…

Solution

The positive value of &#955; for which the co-efficient of x 2 in the expansion x 2 x + &#955; x 2 10 is 720…

Solution

The positive value of λ for which the co-efficient of x 2 in the expansion x 2 x + λ x 2 10 is 720…