Week 6 – Precalc 11

One of the things we learned this week in Precalc 11 is solving quadratic equations ax^2\pm x\pm c=0 using the quadratic formula x=\frac{-b\pm\sqrt{b^2-4ac}}{2a} where a\neq0 because you don’t want to divide the whole thing by 0. This is probably one of the easiest ways to solve a quadratic equation in my opinion.

Ex.
x^2-x-6=0
We know that a=1, b=-1, c=-6 so all we have to do is put those numbers in the formula.
x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}
x=\frac{-(-1)\pm\sqrt{(-1)^2-4(1)(-6)}}{2(1)}
minus -1 is equal to 1, -1 squared is 1, 1 times -6 is -6 times -4 is 24, and 2 times 1 is 2.
x=\frac{1\pm\sqrt{1+24}}{2}
1 plus 24 is 25.
x=\frac{1\pm\sqrt{25}}{2}
square root of 25 is 5
x=\frac{1\pm 5}{2}
we end up with 1\pm 5 which is -4 or 6, divided by 2 so we get
x=-2 or x=3

More Examples

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