(i) 2 x + 9 = 0We have, 2x+9=0⇒2x=−9⇒x=2−9​ which is a linear equation in one variable i.e., x only.Theref ore, x=−29​ is a unique solution on the number line as shown below:(ii) 2x + 9 = 0We can write 2 x + 9 = 0 in two variables as 2 x + 0, y + 9 = 0or x=2−9−0.y​∴ When y=1,x=x=2−9−0(1)​=−29​ y=2,x=2−9−0(2)​=2−9​y=3,x=2−9−0(3)​=2−9​ Thus, we get the following table:Now, plotting the ordered pairs (2−9​,3),(2−9​,3) and (2−9​,3) on a graph paper and joining them, we get a line PQ as solution of 2x + 9 = 0.