Factorise $x^{2} + 7x + 12$ using $(x+a)(x+b)$.

Factorise $x^{2} + 7x + 12$ using $(x+a)(x+b)$.
  1. $(x + 3)(x + 4)$
  2. $(x + 2)(x + 6)$
  3. $(x + 1)(x + 12)$
  4. $(x - 3)(x - 4)$

Solution

Find $a, b$ with $a + b = 7,\ ab = 12$. So $a = 3, b = 4$.

Asked in: IMO

Practice more ALGEBRAIC EXPRESSIONS AND IDENTITIES questions on Aicharya