Question:
Find the solution set of the in equation $|x-1|<2$.
Solution:
$|x-1|<2$
Square both sides
$\Rightarrow(x-1)^{2}<4$
$\Rightarrow x^{2}-2 x+1<4$
$\Rightarrow x^{2}-2 x-3<0$
$\Rightarrow x^{2}-3 x+x-3<0$
$\Rightarrow x(x-3)+1(x-3)<0$
$\Rightarrow(x+1)(x-3)<0$
Observe that when $x>3(x-3)(x+1)$ is positive
And for each root the sign changes hence
We want less than 0 that is negative part
Hence $x$ should be between $-1$ and 3 for $(x-3)(x+1)$ to be negative
Hence $x \in(-1,3)$
Hence solution set for $|x-1|<2$ is $(-1,3)$