There, we gave introduction to Quadratic polynomial, Quadratic Equation, Methods to solve the Quadratic Equations and about Method of Solving by Factoring.
That knowledge is a prerequisite here.
Here, we apply the Method to solve problems. Solved Examples and Exercise problems are given.
Example 1 : How Do You Solve Quadratic
Solve x2 + x - 42 = 0.
Solution of Example 1 How Do You Solve Quadratic :
The Factoring of the LHS of the above Equation is given below.
-*-*-*-*-*-* Let P = x2 + x - 42
In Factoring of Trinomials (Quadratics), we follow the five steps.
Step 1: Coefficient of x2 x constant term = 1 x -42 = -42
Step 2: We have to express -42 as two factors whose sum = coefficient of x = 1 ; -42 = -6 x 7; (- 6 + 7 = 1)
Step 3: P = x2 + x - 42 = x2 + 7x - 6x - 42
Step 4: P = x(x + 7) - 6(x + 7)
Step 5: P = (x + 7)(x - 6)
Thus, By Factoring the Quadratic Polynomial, x2 + x - 42,we get the Factors as (x + 7)(x - 6)
-*-*-*-*-*-*
x2 + x - 42 = 0 ⇒ (x + 7)(x - 6) = 0 ⇒ (x + 7) = 0 or (x - 6) = 0 (x + 7) = 0 ⇒ x = -7 (x - 6) = 0 ⇒ x = 6 Thus, x = -7, 6 are the two roots of the given Quadratic equation. Ans.
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Solution of Example 2 of How Do You Solve Quadratic :
The Factoring of the LHS of the above Equation is given below.
-*-*-*-*-*-* Let P = 12 - 4x - 5x2 = -5x2 - 4x + 12
In Factoring of Trinomials (Quadratics) , we follow the five steps.
Step 1: Coefficient of x2 x constant term = -5 x 12 = -60
Step 2: We have to express -60 as two factors whose sum = coefficient of x = -4 ; -60 = -10 x 6; (-10 + 6 = 4)
Step 3: P = -5x2 - 4x + 12 = -5x2 - 10x + 6x + 12
Step 4: P = -5x(x + 2) + 6(x + 2)
Step 5: P = (x + 2)(-5x + 6)
Thus, By Factoring the Quadratic Polynomial, 12 - 4x - 5x2,we get the Factors as (x + 2)(-5x + 6)
-*-*-*-*-*-*
12 - 4x - 5x2 = 0 ⇒ (x + 2)(-5x + 6) = 0 ⇒ (x + 2)= 0 or (-5x + 6) = 0 (x + 2) = 0 ⇒ x = -2 (-5x + 6) = 0 ⇒ -5x = -6 ⇒ x = -6⁄-5 = 6⁄5 Thus, x = -2, 6⁄5 are the two roots of the given Quadratic equation. Ans.
Exercise : How Do You Solve Quadratic
Solve x2 + x - 30 = 0.
Solve 6 - x - 2x2 = 0.
For Answers See at the bottom of the Page.
NOTE: You may solve all these problems of Exercise using Quadratic Formula, after learning it.
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