2. Doesn't it mean that you can't write squares at the back, but generally squares and cubes? ,? Written in the middle and upper part of lg, ㏒, ㏑ and real numbers.

Like lg? 2

3.㏑ is the logarithm of ㏒ e basis, that is ㏒ ex = ㏑ x.

As long as you know that e≈2.7 in high school mathematics is often used to compare sizes, it can be eliminated even if you participate in the calculation, which is relatively simple.

1.lg5*lg20=lg﹙ 10÷2﹚×lg﹙ 10×2﹚=﹙lg 10-lg2﹚×﹙lg 10+lg2﹚=﹙ 1-lg2﹚×﹙ 1+lg2﹚= 1-lg？ 2