Question: Factorise:
x2 − 11x − 42
Solution:
The given expression is $x^{2}-11 x-42$.
Find two numbers that follow the conditions given below :
Sum $=-11$
Product $=-42$
Clearly, the numbers are $-14$ and 3 .
$x^{2}-11 x-42=x^{2}-14 x+3 x-42$
$=x(x-14)+3(x-14)$
$=(x-14)(x+3)$
