News Letter 1

Here is My first News Letter using LetterPop.

Two Types of Quadratic Formula

When I was a high school student in Korea, I learned two types of quadratic formula.

If the quadratic equation is in the form of   .

As you know, the first quadratic formula is the famous  .

We learned one more thing. The other one is used only if b is a even number. 

If we let b be 2d in the quadratic equation, it will be  , right?

Then, the new quadratic formula becomes . 

You already figured out how I got the second one!!

If we substitute 2d into b in the original quadratic formula,

we could get  ,

which is  and we can just reduce them.

And finally got the new quadratic formula   ,

when the quadratic equation is .

Do you know why we used two types of quadratic formula in Korea? We had to solve all the math problems mentally without any calculator in a short time. Believe or not, the second quadratic formula sometimes helped me a lot to save time! 

You can try it now.

Solve   using the second type of  quadratic formula 

(Hint: in this case, d becomes 12/2, which is 6)