First slide
Binomial theorem for positive integral Index
Question

If the middle term in the expansion of x2+28is 1120, then the product of possible real values of x is ____.

Moderate
Solution

Middle term is n2+1th , i.e., (4+1)th , i.e., T5
 T5=8C4x24×24=1120
or    x4=8×7×6×51×2×3×4x4=1120
x4=112070=16x2+4x24=0
Therefore, x=±2 only as xR

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