Homework Clinic
Mathematics Clinic => Grade 10 Mathematics => Topic started by: j_sun on Jun 17, 2013
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i know how to find the vertex and axis of semetry, but idkk how to find the roots without graphing! please helppp (:
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A root is also called the "zero."
Factor it out, set it equal to zero, ta-da!
Example:
y = x^2 + 6x + 8
y = (x + 4)(x + 2)
x + 4 = 0
x = -4
x + 2 = 0
x = -2
Plug it in to your long equation, it should equal 0:
y = (-2)^2 + 6(-2) + 8 = 4 - 12 + 8 = 0
y = (-4)^2 + 6(-4) + 8 = 16 - 24 + 8 = 0
Yay!
Edit: Quadratics always have 2 roots, although some times they are the same number (a "double root").
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factoring is one method, but it is not always easy to come up with the factors. Another is Completing the Square, which is a technique of manipulating the equation into an equivalent equation that is easier to find the roots of. The Quadratic formula solves quadratics of the form:
ax^2 + bx + c = 0. It is derived by completing the square on this equation resulting in:
x = (-b +/- (b^2 - 4ac)^.5)/2a
+/- means plus or minus
^.5 means to the 1/2 power (the square root)
try searching on "completing the square" to get a description of the technique.