Here is 1 example.
Mrs. Jacinto asked a carpenter to construct a rectangular bulletin board for her classroom. She told the carpenter that the board’s area must be 18 square feet. Suppose the length of the board is 7 ft. longer than its width.
Area = l x w
18 = x(x+7)
18 = x²+7x
18 + 49/4 = x²+7x+49/4 this is a quadratic equation.
and there are other more real life situation w/ uses quadratic equation but the solution is more complicated.