justaguide | College Teacher | (Level 2) Distinguished Educator

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The quadratic formula is used for a quadratic equation of the form ax^2 + bx + c = 0 when it is not possible or very difficult to factorize the expression ax^2 + bx + c.

Here, to find the roots x1 and x2 which are usually irrational or complex we use the following relations:

x1 = [-b + sqrt (b^2 - 4ac)]/2a

x2 = [-b - sqrt (b^2 - 4ac)]/2a

giorgiana1976 | College Teacher | (Level 3) Valedictorian

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We know that the quadratic formula for finding the roots of the quadratic equation is:

x1 = [-b + sqrt(b^2 - 4ac)]/2a

x2 = [-b - sqrt(b^2 - 4ac)]/2a

We know that the expression under the square root  is called the discriminant of the quadratic, delta.

If delta is positive, the equation has 2 real distinc roots.

If delta is zero, the equation has 2 equal real roots.

We'll compute delta. For this reason, we'll identify a,b,c:

a = 1 , b = 7 , c = 9

delta = 49 - 36

delta = 13 > 0

Since delta is positive, the equtaion has 2 real distinct roots:

x1 = (-7+sqrt 13)/2

x2 = (-7-sqrt 13)/2