#chp3 series and sequences

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waxen pawn
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u can find the first term

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U_n = a + (n-1)d

solemn wolf
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chp3?!

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chapter 3 of which module

waxen pawn
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yk that U_20 = a + 19d

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and d = -1

solemn wolf
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core pure ?

waxen pawn
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and U_20 = 14

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so
14 = a - 19
a = 33

solemn wolf
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oh

solemn wolf
waxen pawn
high path
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Find 2 expressions and do simultaneous equations to find a or d, then substitute what you found (a/d) into one of the expressions to find the other (a/d). Now you have a and d, substitute into 'a+9d' to find the 10th term.

grizzled condor
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It means the sum of n terms in a series e.g 1,2,3,4 is our series S_3=6 (1+2+3)