For what value is a is (a, 9) a solution of the equation y=2x+1

a = 4

Step-by-step explanation:

y = 2x + 1 ... (1)

Going through y - y1 = m (x - x1)

m is slope and it is 2

y1 = 9 and x1 = a

y - 9 = 2 (x - a)

y - 9 = 2x - 2a

y = 2x - 2a + 9 ... (2)

Equating (1) and (2)

2x + 1 = 2x - 2a + 9

Collecting like terms

2x - 2x + 2a = 9 - 1

2a = 8

a = 8/2

a = 4