The area of a parallelogram is given by the formula a=bh the area of the parallelogram on the right is 126 sq units. find its base and height

From the diagram we have

Base = 
Height = 

Area = Base × Height
126 =  ⇒ Expand the double bracket
126 =  ⇒ Subtract 126 both sides
0 =  ⇒ Factorise the quadratic expression
0 =  ⇒ Equating each factor to zero

                      
                          

We need the positive value of  so we use 

Height = 5+1 = 6
Base = 4(5)+1 = 21