The roots of the quadratic equation (x+β)(x−α)=0 are:
α,−β
Observe that the equation is already factorized and we also know that the root of an equation is that value which satisfies the equation.
Since a product of two factors would be zero when either of the factors is zero [or both of them zero], we shall equate the factors to zero.
(x+β)(x−α)=0
which means, (x+β)=0 or (x−α)=0
x=−β or x=α
The roots of given equation are α,−β.