Question

If ax + 3y = 12 has an X intercept of 4, find the value of a. Hence find the Y intercept of the line. [4 MARKS]

Answer 1

Concept : 1 Mark
Calculation : 1 Mark
Value of a : 1 Mark
Y-intercept : 1 Mark

Since the line has an X intercept of 4, we can say that (4, 0) is a solution of the equation

ax + 3y = 12

Putting x = 4, y = 0 in the above equation, we get

4a + 0 = 12

4a = 12

a = 3

Thus, the equation of the line is 3x + 3y = 12

Simplifying, we get x + y = 4

At the Y intercept, x = 0

Putting x = 0 in the above equation, we get y = 4

Thus, the Y intercept of the line is 4