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5.12 Solving Quadratic Equations by Factoring Algebra I. Zero-Factor Property. Let a and b be real numbers, variables or algebraic expressions and factors such that a*b=0; THEN a = 0 or b= 0. This property also applies to three or more factors. Zero Factor property.
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Zero-Factor Property • Let a and b be real numbers, variables or algebraic expressions and factors such that a*b=0; THEN a = 0 or b= 0. • This property also applies to three or more factors.
Zero Factor property • This property is the primary property for solving equations in algebra • For example, to solve the equation (x-1)(x+2) = 0 you can use the zero factor property to conclude that either x-1=0 or x+2 = 0. • If we set the first factor to 0, x = 1; if we set the second factor to 0, x = -2 • So the equation (x-1)(x+2) =0 has exactly two solutions : 1 and -2. • You can check your answers.
Quadratic equation • A quadratic equation is an equation that can be written in the general form • ax2 + bx + c = 0 where a, b and c are real numbers and a does not equal 0. • You are going to combine your factoring skills with the Zero-Factor property to solve quadratic equations.
Steps for solving quadratic equations • Write the quadratic equation in general form. • Factor the left side of the equation. • Set each factor with a variable equal to zero. • Solve each linear equation • Check each solution in the original equation
Solving equations • (s-4)(s-10) = 0 • X2-144 = 0 • 6x2 + 3x = 0 • y(y-4) + 3(y-4)=0
More Examples 1) 2) 3) 4) 5)
Quadratic equation with a repeated solution • If you have a perfect square trinomial, your factors are the same…so, you will only have one solution • x2-8x + 16=0 • Factor: (x-4)(x-4) • Set x-4 = 0 • x = 4
Solving a quadratic equation by factoring • Solve (x+1)(x-2) =4 • Don’t make the mistake of setting x+1 equal to 4. You must first satisfy the zero property rule, so you need to do FOIL and then factor and set to zero! • x2-x-2=4 so x2-x-6 = 0 • (x-3)(x+2) = 0, so x = 3 and x = -2