waecmaths question:
The nth term of a sequence is ${{T}_{n}}=5+{{(n-1)}^{2}}$. Evaluate ${{T}_{4}}-{{T}_{6}}$
Option A:
30
Option B:
16
Option C:
–16
Option D:
–30
waecmaths solution:
$\begin{align} & {{T}_{n}}=5+{{(n-1)}^{2}} \\ & {{T}_{4}}=5+{{(4-1)}^{2}}=5+{{3}^{2}}=14 \\ & {{T}_{6}}=5+{{(6-1)}^{2}}=5+{{5}^{2}}=30 \\ & {{T}_{4}}-{{T}_{6}}=14-30=-16 \\\end{align}$
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