1. log₅12,5+log₅2 2. lg700000₋lg7 3. log₅75-log₅15

Question

1. log₅12,5+log₅2
2. lg700000₋lg7
3. log₅75-log₅15

Answer 1

1. log₅(25/2) + log₅2 = log₅25 - log₅2 + log₅2 = log₅25 = 2
2. lg 700000 - lg7 = lg7 + lg 100 000 -lg7 = lg100 000 = 5
3. log₅75 - log₅15 = log₅(15 · 5) - log₅15 = log₅15 + log₅5 - log₅15 = log₅5 = 1