#812 · Algebra · Sequences & series

Sum of mixed linear progression

Find the sum of the first 21 terms of the progression $\frac{a + b}{2}$ , $a$ , $\frac{3 a - b}{2}$ , \dots .

~4 minAnswer checked instantlyarithmetic progressionalgebraic expressions

H. S. Hall & S. R. Knight, Higher Algebra (1891) · Ch. IV. Arithmetical Progression, Examples IV.a, No. 12

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