(lg8+lg1000)lg5+3(lg2)²
=(lg2³+lg10³)lg5+3(lg2)²
=(3lg2+3lg10)lg5+3(lg2)²
=(3lg2+3)lg5+3(lg2)²
=3lg2lg5+3lg5+3(lg2)²
=3lg2(lg2+lg5)+3lg5
=3lg2+3lg5
=3(lg2+lg5)
=3
(lg8+lg1000)lg5+3(lg2)²
=(lg2³+lg10³)lg5+3(lg2)²
=(3lg2+3lg10)lg5+3(lg2)²
=(3lg2+3)lg5+3(lg2)²
=3lg2lg5+3lg5+3(lg2)²
=3lg2(lg2+lg5)+3lg5
=3lg2+3lg5
=3(lg2+lg5)
=3