00:01
When we're solving an equation that have a highest exponent of two, those are called quadratics, and we have four different techniques at least to solve quadratic equations.
00:11
In this particular problem, this is a quadratic.
00:15
The highest exponent would be two.
00:17
And what we would normally do is to foil this piece, distribute this negative six, collect our like terms, and have a quadratic without all of these parentheses.
00:30
And then choose one of our techniques to solve it, and that will work.
00:35
However, there's a lot of steps, and more steps means more errors sometimes.
00:40
So there's a little bit shorter way to do this, and what it is is we call this u substitution, where we substitute u in different variables or different values in the original problem.
00:54
We choose the u by being the sort of the middle term without the coefficient.
01:01
So i'm going to let the u be this 3x plus 4.
01:06
And if i substitute the u in to this problem, you see that i get u squared minus 6 u plus 9 equals 0.
01:18
And this is also in quadratic form, but a lot easier quadratic than what the one we had before...