Question

If x= 2/3 and x = – 3 are roots of the quadratic equations ax2 + lx + b = 0, find the values of a and b.

Answer 1

Explanation:

ax² + 7x + b

Substituting 2/3 in equation

4a/9 + 14/3 +b = 0

4a/3 + 14 + 3b = 0

4a + 42 + 9b = 0 ------> (i)

Substituting -3 in equation

9a - 21 + b = 0

81a - 189 + 9b = 0 ------> (ii)

Elimination method

a = 3

substituting in any equation

b = -6