Sequence 2

Algebra Level 4

If the coefficient of $x$ in the expansion, $\displaystyle \prod_{r=1}^{110} (1+rx)$ is equal to $\lambda (1+10)(1 + 10 + 100)$ , find $\lambda$ .

The answer is 5.

1 solution

First Last
Dec 18, 2015

It can be found by looking at results of (1 + x)(1 + 2x)... that the coefficient of x is the sum of numbers up to the number of roots, in this case 110. So 1+2+...+110 = 6105. Then λ(1221) = 6105. λ = 5

Sequence 2

The answer is 5.

1 solution

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