Question

Use identity (x+a)(x+b)=x^2+(a+b)x+ab to find the product of (4x+5)(4x-1).

Answer 1

(x+a)(x+b)=x^2+(a+b)x+ab
Given :(4x+5)(4x-1)
Using the above identity ,
=> (4x)^2+(5-1)4x+(5)(-1)
=> 16x^2+16x-5