Question

Factor.f(x) = x² - 2x - 8=(x + [?])(x − [])

Answer 1

`\begin{gathered} f(x)\text{ = x}^2\text{ - 2x -8} \\ f(x)\text{ = \lparen x - 4\rparen\lparen x+2\rparen} \end{gathered}`
`\begin{gathered} Quadratic\text{ Formula is in the form} \\ ax^2\text{ + bx +c} \\ If\text{ we expand the brackets \lparen x+?\rparen\lparen x-?\rparen we get x}^2\text{ -2x -8} \\ a\text{ = 1 b = -2 c = -8} \\ The\text{ x must multiply together to give ac. } \\ The\text{ other two numbers must add to get b and must be factors of 8} \\ In\text{ this case, 4 and two are factors of 8. if we say -4 +2 the answer = -2 =b.} \\ Thus\text{ 4 and -2 are our factors.} \\ \end{gathered}`