The solution set of 3x−41=121 is....
Explanation
First change it so that the fractional form disappears
3x−41=121
124x−3=121
∣4x−3∣=1
Its definition is
∣4x−3∣={4x−3,−(4x−3),for x≥43for x<43
For x≥43 then
∣4x−3∣=1
4x−3=1
4x=4
x=1
For x<43 then
∣4x−3∣=1
−(4x−3)=1
−4x+3=1
−4x=−2
x=21
So the solution set is {21,1}.