Topic 10.1
(Quadratic Equations I) (Factoring, Square Root Property)Factoring
The quadratic equation - ax2 + bx + c = 0ax2 = Quadratic Term bx = Linear Term c = Constant
Factoring - Move all terms to one side of the equation and have zero on the
other. Factor the side with the terms and set all factors equal to zero.
x2 + 6 = 5x Move the 5x to the left side of the equation and put it in
middle, (change sign of 5x) so there is decreasing exponents of x.
x2 - 5x + 6 = 0 Factor the left side of the equation.
(x - 3)(x - 2) = 0 Set each factor equal to zero and solve.
x - 3 = 0 x - 2 = 0
x = 3 x = 2 {2 ,3} Answer
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4x2 - 12x + 9 = 0 Factor the left side of the equation.
(2x - 3)2 = 0 Set each factor equal to zero.
2x - 3 = 0 2x - 3 = 0
2x = 3 2x = 3 Only use one 3/2 in your
x = 3/2 x = 3/2 answer, as an element of a set
{3/2} Answer is never used more than once).
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3r(4r - 7) - 2 = 4 Multiply using the distributive property and move
all terms to the left side of the equation.
12r2 - 21r - 2 - 4 = 0 Combine like terms.
12r2 - 21r - 6 = 0 Factor the left side of the equation.
3(4r2 - 7r - 2) = 0
3(4r + 1)(r - 2) = 0 Set all factors equal to zero.
3 = 0 4r + 1 = 0 r - 2 = 0
no answer 4r = -1 r = 2
r = -¼ r = 2 {-1/4 , 2} Answer
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x3 + 2x2 - 15x = 0 Factor the left side of the equation.
x(x2 + 2x - 15) = 0
x(x + 5)(x - 3) = 0 Set all factors equal to zero.
x = 0 x + 5 = 0 x - 3 = 0
x = 0 x = -5 x = 3 {-5, 0, 3} Answer - When all the terms of the left
side of the equation contain the variable you are solving for, one answer is 0. If
the degree of the equation is 3, then there are 3 answers.
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Square Root Property - These equations will have only two terms, after all terms
are combined. (ax2 + c = 0) There will be only a quadratic term(ax2)and a
constant term [c]. Combine all like terms and move the constant term to
the opposite side of the equation and then take the square root of both
sides of the equation.
x2 - 5 = 0 Move the 5 to the right side of the equation.
x2 = 5 Take the square root of both sides of the equation.
REMEMBER TO PUT A ± IN FRONT OF THE ANSWER.
X = ± 5 {± 5} Answer
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2x2 - 162 = 0 Move the 162 to the right side of the equation.
2x2 = 162 Divide both sides of the equation by 2.
x2 = 81 Take the square root of both sides of the equation.
x = ± 9 {± 9} Answer
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(x - 4)² = 225 Take the square root of both sides.
x - 4 = ±15 Remember to put a ± in front of the 15.
x = 4 ± 15 Move the 4 to the right side of the equation.
4 + 15, 4 - 15 Two answers
19 -11 {-11, 19} Answer
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25x² - 40x + 16 = 75 Factor the left side of the equation. It must factor
(5x - 4)² = 75 into a binomial squared.
5x - 4 = ± Ö 75 Take the square root of both sides.
5x = 4 ± Ö 75 Move the four to the right side of the equation.
x = (4 ± Ö 75) / 5 Divide both sides of the equation by 5.
Your answer is a fraction with 4 ± Ö75 in the
numerator and 5 in the denominator.
Ö75 means square root of 75.