7.3 Notes FACTORING QUADRATICS
What do we know about quadratics? Have an x 2 ax 2 + bx + c Degree is 2 Has 2 roots/x-intercepts/solutions Make a parabola
Factoring: FIRST check for... Anything that the terms have in common Numbers & variables 2x 2 – 32x 2x(x-16) 3x x – 27 3(x 2 + 6x – 9) -12x -3(4x 2 – 9)
Difference of Squares (b = 0) Subtraction of 2 squared terms x 2 – 4 Square root each piece into two sets of binomials Separate with addition and subtraction x 2 – 4 (x + 2)(x – 2) -12x -3(4x 2 – 9) -3(2x + 3)(2x – 3)
Factoring Quadratic Trinomials(a = 1) Quadratics with 3 terms Find 2 numbers which multiply to the term with no x but add to the middle term. x 2 + 5x + 6 2 and 3 because 2*3 = 6 and = 5 (x + 3)(x + 2) x 2 – 8x – 20 -10*2 = - 20 and = - 8 (x – 10)(x + 2)
Factoring when a is NOT 1 2x 2 + 5x + 3 Make a chart Multiply a and c and place on one side Place b on the other side Find numbers that multiply to be the same as the left column but add to the right column. Rewrite the original but changing the middle term to your 2 new numbers being added. 2x 2 + 2x + 3x + 3 Break into 2 groups and factor out common factors. 2x(x + 1) + 3(x + 1) Factor out the common group and leave the rest in the other. (x + 1)(2x + 3) a*cb 65 2*3 = = 5
Factor each of the following 7x 2 + 9x x(7x + 9) 12x 2 – 36 12(x 2 – 3) 9x 2 – 100 (3x + 10)(3x – 10) 36x 2 – 144 36(x 2 – 4) 36(x + 2)(x – 2) x 2 – 11x + 30 (x – 6)(x – 5) x 2 + 7x – 18 (x + 9)(x – 2) 9x 2 – 9x – 10 9x 2 – 15x + 6x – 10 3x(3x – 5) + 2(3x – 5) (3x – 5)(3x + 2) *10 = = 1 -15* = -9