`2)a)5^(x+2)+5^(x+1)+5^x+225=1000`
`=>5^(x+2)+5^(x+1)+5^x=1000-225`
`=>5^x . 5^2+5^x . 5^1+5^x . 1=775`
`=>5^x .(25 + 5 + 1)=775`
`=>5^x .31==775`
`=>5^x=775:31`
`=>5^x=25`
`=>5^x=5^2`
`=>x=2`
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