How do you factor $4-49z^2$ ?

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Answer 1 · 2015-11-27T17:28:33

$(2+7z)(2-7z)$

The expression if the difference of two squares

$(a+b)(a-b)=a^2-ab+ab-b^2=a^2-b^2$

In this case

$a=2$ , $a^2=4$

$b=7z$ , $b^2=49z^2$

How do you factor 4-49z^24-49z^2?