Factorize each of the following quadratic polynomials by using the method of completing;
4y2 + 12y + 5
We have 4y2 + 12y + 5 = 4 (y2 + 3y + 
) [Therefore, coefficient of y2 = 1]
= 4 [y2 + 3y + (
)2 – (
)2 + 
]
= 4 [(y + 
)2 – 12] (Completing the square)
= 4 (y + 
+ 1) (y + 
– 1)
= (2y + 5) (2y + 1)
3