Respuesta :
[tex]\\ \sf\ast\Rrightarrow x^2-400[/tex]
[tex]\\ \sf\ast\Rrightarrow (x)^2-(20)^2[/tex]
- a^2-b^2=(a+b)(a-b)
[tex]\\ \sf\ast\Rrightarrow (x+20)(x-20)[/tex]
Step-by-step explanation:
- x²-400
- (x)²-(20)²
By the formula, [a²-b²=(a+b)(a-b)]
- (x+20)(x-20)
Hence, first option is correct