Question

If two of the zeroes of the cubic polynomial ax³ + bx² + cx + d are 0, then the third zero is

(a) \(\frac{-b}a\)

(b) \(\frac{b}a\)

(c) \(\frac{c}a\)

(d) \(\frac{-d}a\)

Answer 1

(a) \(\frac{-b}a\)

Let α , 0 and 0 be the zeroes of ax³ + bx² + cx + d = 0

Then the sum of zeroes = \(\frac{-b}a\)

⇒ α + 0 + 0 = \(\frac{-b}a\)

⇒ α = \(\frac{-b}a\)

Hence, 

the third zero is \(\frac{-b}a\)