Answer :

luana
[tex]x^2-3x-4=0\\\\x^2-3x-4=\\x^2+x-4x-4=\\x(x+1)-4(x+1)=\\(x+1)(x-4)\\\\(x+1)(x-4)=0,\ when:\\\\x+1=0\ \ \ \ \ \ \ \ or\ \ \ \ \ \ \ x-4=0\\x=-1\ \ \ \ \ \ \ \ \ \ \ or\ \ \ \ \ \ \ x=4[/tex]
x² - 3x - 4 = 0

Reverse FOIL method . . .

(x - 4)(x + 1) = 0

one of the paranthesis has to be equal to zero if the other is not . . .

x - 4 = 0

x = 4

x + 1 = 0

x = -1

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