For x∈(−261,261), 24x2<1
So tan−1(4x)+tan−1(6x)=tan−1(1−24x210x)=6π.
1−24x210x=31⇒24x2+103x−1=0.
x=48−103±300+96=24−53±311.
x1=24−53+311≈0.054 (valid, lies in range).
x2=24−53−311≈−0.776 (rejected, outside range).
Number of solutions =1.