GRADE 11 math help please?

Question

the harmonic mean of 2 numbers, a and b is 2/ 1/a+1/b

The harmonice mean of 3 numbers a,b, and c is
3/ 1/a + 1/b + 1/c

a) simplifyt the expressions for 2 and 3 numbers and find a simplified expression for the harmonic mean of 4 numbers.

b) find the harmonice mean of the numbers 2,3,4,7,9

Answer 1

Multiply the numerator and denominator by ab, abc, or abcd as the case may be. That clears the fractions in the denominator, which is what you need to do to simplify.