When particle gains whole of potential energy in the form of kinetic energy at x=−3m, then it will travel maximum distance till whole of its kinetic energy becomes zero. i.e., ‌‌K=U=0 ⇒‌‌2−20x+5x2=0 5x2−20x+2=0
∴‌‌x=‌
−(−20)±√(−20)2−4×5×2
2×5
=‌
20±√360
10
=‌
20±18.97
10
x=2±1.9 For maximum value of x, taking + ve sign x=2+1.9=3.9 ∴ Total distance =|−3|+39 =6.9m≃7m