Answer:
difference of square identity
Step-by-step explanation:
[tex]21 = 25 - 4[/tex]
25 can be written as [tex]5*5=5^2[/tex]
4 can be written as [tex]2*2=2^2[/tex]
[tex]25 - 4=5^2-2^2[/tex]
WE use difference of square identity
[tex]a^2-b^2=(a+b)(a-b)[/tex]
[tex]5^2-2^2=(5+2)(5-2)[/tex]
[tex]21 = 25 - 4[/tex]
[tex]21=5^2-2^2[/tex]
[tex]21=(5+2)(5-2)[/tex]
[tex]21=(7)(3)[/tex]
21=21 Hence proved.
We proved it using difference of squares identity
