# maths

the first three terms of an a.p are x,2x+1 and 5x-1.find x and the sum of the first 10 terms

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1. 2x-1;3x;5x-2
5x-2-3x=3x-(2x-1)
x=3
S = ½(2a + (n-1)d)n
5*3-2=13
3x=9
13-9=4

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2. 2x+1 - x = 5x-1 - (2x+1)
find x. Now you know that a=x and d=x+1
S10 = 10/2 (2a+9d)

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