Question 167475
{{{28=V[0]+a(4)}}} eq 1
{{{43=V[0]+a(7)}}} eq 2

subtract 2nd equation values from 1st equation to eliminate {{{V[0]}}}

{{{-15=-3a}}} divide by -3 {{{highlight(a=5)}}}

plug a's value into either equation to find {{{V[0]}}}.

{{{43=V[0]+7(5)}}}--->{{{highlight(V[0]=8)}}}