Trying to find an equation

Question

The first number in the third row of this triangular number pattern is 5. If this pattern is continued, what is the first number in the 10th row? the first number in the 100th row. Describe the pattern you see to explain your answer. 

 

so in a triangle starts with 

                 1                Row 1 

              2 3 4              Row 2 

           5 6 7 8 9           Row 3 

    10 11 12 13 14 15 16 

 

how can I find the first number in the  100th row ? can somene please tell me the equation 

 

Answer 1

y = (r - 1)² + 1

 

where r is the row number. Plug in a row number for r to get y, the first number in that row.