alanforde800Maximus wrote:In the infinite sequence a1, a2, a3, ... an where an= n^2, what is a1,323 - a1,322 ?
a) 2245
b) 2645
c) 5290
d) 5545
e) 5790
Every test-taker should know the following identity:
x²-y² = (x+y)(x-y).
The sequence is defined as follows:
a� = 1²
a₂ = 2²
a₃ = 3²
And so on.
Thus:
a�₃₂₃ - a�₃₂₂ = 1323² - 1322² = (1323+1322)(1323-1322) = (2645)(1) = 2645.
The correct answer is
B.
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