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## Homework Statement

How many terms are needed in the series 11+16+21+26...+ to exceed 450

d=5

## Homework Equations

S

_{n}=n/2(2u

_{1}+(n-1)d)

## The Attempt at a Solution

(455 because is term exceeding 450 by the d of 5)

455=n/2(22+5n-5)

455=17n+5n

^{2}

455/17=5n

^{2}

Calculator work,

but the answer I get is not 12. The textbook says the answer is 12 :(