multiplying

Question

(4x + 5)²

Answer 1

(4x + 5)²

(4x + 5)(4x + 5)       definition of square

(4x)(4x) + (4x)(5) + (4x)(5) + (5)(5)   FOIL

16x² +20x + 20x + 25     simplify

16x² + 40x + 25             combine like terms

Answer 2

Use F-O-I-L (First-Outside-Inside-Last):

  (a + b)(c + d)

   First      Outside    Inside       Last

    ac    +     ad    +    bc     +    bd

 

Now, realize that:

    (4x + 5)² = (4x + 5)(4x + 5)    and use F-O-I-L