Question
Solve the inequality with square root
\sqrt{3-x}-\sqrt{x+1}>\dfrac{1}{2}
for real values of x
Solve the inequality with square root
\sqrt{3-x}-\sqrt{x+1}>\dfrac{1}{2}
for real values of x
First for the square roots to be real values,
3-x\geq 0 and x+1\geq 0
The x is confined in the range of
-1\leq x\leq 3
Now let’s introduce an intermediate variable
Let t=\sqrt{x+1}, (0\leq t\leq 2)
Then, x=t^2-1
The original inequality can be converted to an inequality in terms of t
\sqrt{4-t^2}>\dfrac{1}{2}+t
Square both sides of the inequality
4-t^2>\dfrac{1}{4}+t+t^2
2t^2+t-\dfrac{15}{4}<0
Considering the domain of t,solve the quadratic inequality
0 < t<\dfrac{\sqrt{31}-1 }{4}
0 < t^2 < (\dfrac{\sqrt{31}-1 }{4} )^2
-1 < t^2-1 < (\dfrac{\sqrt{31}-1 }{4} )^2-1
-1 < x < (\dfrac{\sqrt{31}-1 }{4} )^2-1
-1 < x <1-\dfrac{\sqrt{31} }{8}