Question

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

A.9
B.8
C.6
D.4

Answer 1

X=a Y=9

y=2x+1
9=2x+1
9-1=2x+1-1 (subtract both side with -1)
8=2x+0
8=2x
8/2=2x/2 (divide both side with 2)
4=X

Hope this helps!

Answer 2

D. 4 is your answer. 9 is the y value so you set up the equation as 9 = 2x+1. Subtract 1 from each side to get 8 = 2x. Then divide both sides by 2 to get x = 4.