Question 618996
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Hi,
5x-3, x+2 and 3x-11 form an arithmetic progression..
{{{a[1] = 5x-3}}}
{{{a[2] = (5x-3) + d = x+2 }}}  d = -4x + 5
{{{a[3] = (5x-3) + 2(-4x+5) = 3x-11 }}}  -6x = -18 , x = 3, {{{a[1] = 12}}} and d = -7
{{{a[21] =  12 + 20(-7) = -128}}}