Factorise:

The given expression is $3 m^{2}+24 m+36$.

Find two numbers that follow the conditions given below:

Sum $=24$

Product $=36 \times 3=108$

Clearly, the numbers are 18 and 6 .

$3 m^{2}+24 m+36=3 m^{2}+18 m+6 m+36$

$=3 m(m+6)+6(m+6)$

$=(3 m+6)(m+6)=3(m+2)(m+6)$