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Quadratic formula

November 12, 2019

Today’s the big day in grade 10! Here’s the derivation of the quadratic formula. It shows how to complete the square for any trinomial, and then, to set y=0 and isolate x to find the roots, as we’ve been practicing lately.

we isolate x by doing opposite operations on both sides.

In the end, we have a beautiful formula (in the box) which we will use a lot. We even learned how to sing this formula to the tune of “pop goes the weasel”.

We use the formula to calculate roots of a quadratic.

We could have done the same thing by factoring

But not all equations are factorable. We can always use the formula!

We also saw what happens when there are no roots

We will be using this a lot to solve problems tomorrow.

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