Solution:
Given,… (1)
… (2)
… (3)
… (4)
We know that an equation is a mathematical statement that two things are equal. It consists of two expressions, one on each side of the sign of equality.
Thus, the sign ‘=’ should be present to show the equality between the two expressions.
In (1), (2) and (3), the two expressions are separated by ‘=’, so these are equations.
But in (4), there is only one expression with no ‘=’ in between.
Therefore, (4) is not an equation.
Hence, the correct option is 4.
