Question

Please can somebody tell me what happened in the 2nd last step? Please its urgent.

Answer 1

Answer:

0÷something=0

Step-by-step explanation:

m-n shifted to right hand side

0÷m-n=0

so that a+(m+n-1)d is remained.

Answer 2

hey mate

it is simple just see that the RHS has zero and in LHS there is a product of two terms.

The criteria for a product of two terms to be zero is that one term from those two must be zero.

so here, the writer put the same criteria in (m-n) and (a+(m+n-1)d).

he made cases that case 1

m-n = 0

but it m can not be equal to n so the other term was equated to zero.

hope it helped you out

please mark it as the brainliest answer