Question:
Factorize each of the following algebraic expression:
x2 − 22x + 120
Solution:
To factorise $\mathrm{x}^{2}-22 \mathrm{x}+120$, we will find two numbers $\mathrm{p}$ and $\mathrm{q}$ such that $\mathrm{p}+\mathrm{q}=-22$ and $\mathrm{pq}=120$.
Now,
$(-12)+(-10)=-22$
and
$(-12) \times(-10)=120$
Splitting the middle term $-22 \mathrm{x}$ in the given quadratic as $-12 \mathrm{x}-10 \mathrm{x}$, we get:
$\mathrm{x}^{2}-22 \mathrm{x}+12=\mathrm{x}^{2}-12 \mathrm{x}-10 \mathrm{x}+120$
$=\left(\mathrm{x}^{2}-12 \mathrm{x}\right)+(-10 \mathrm{x}+120)$
$=\mathrm{x}(\mathrm{x}-12)-10(\mathrm{x}-12)$
$=(\mathrm{x}-10)(\mathrm{x}-12)$