X2 + 7x - 18 select one of the factors of the quadratic expression. a) (x+2) b) (x+6) c) (x-2) d) (x-6)

The right answer is C) (x - 2).

Step-by-step explanation:

Given x² + 7x -18 , to find the correct factor you have to apply Baskhara´s equation

x = [-b ± √(b²- 4·a·c)]/2·a where a,b and c are the coeficietns of the quadratic equation, with a= 1, b= 7 and c= -18.

When you replace each term on the formula, you have

x= [-7 ± √(7² - 4·1·(-18)]/ 2·1 ⇒ x = [-7 ÷ √121]/2 ⇒ then you will find two solutions x1 and x2.

x1 = (-7 + 11)/2 ⇒ x1= 2

x2 = (-7 - 11)/2 ⇒x2=-9

Here you have the factors of the given equation.

So, x² + 7x -18 = (x-2) · (x +9).

Summarizing, the correct option is C) (x - 2)

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answer: -1

step-by-step explanation: