Perfect Square of Quadratic Trinomials Negative Linear Term
Transcript
14! okay! Again we’re going to do the same kind of thing but see how this is plus and this is negative because that’s a negative guys we should make negative negative to make positive, don’t we?
So this time I’m going to use the same factors but with x and x and this time, I’m going to use negative 3 and negative 3 because I know that negative 3 times negative 3 makes positive 9. And if you cross multiply you get negative 3x, cross multiply get negative 3x but remember guys negative 3x minus 3x is negative 6x which is exactly the same as what we have here, okay? So make sure these two are both negative if this happens to be a negative and this is a positive.
So we draw our factorization x minus three times x minus three, we have two of the same kind so it’s x minus three squared all right? But first of all 25 is five times five, isn’t it? And I know that five plus five is ten, so but I make sure they’re both negative though because it’s must be negative ten, so I put x and x and negative five and negative 5.
Cross multiply, you get negative 5x, negative 5x and if you add them negative 5x minus 5x is negative 10x which is what we have here okay that’s why we have to put negative negative on both. So it’s going to be x minus 5, x minus 5 which is x minus 5 squared, all right? That’s the perfect square. Usually, perfect squares are I think are a little bit easier
17! All right. Again, x and x, I know that 144 is 12 times 12 and I know that 12 plus 12 is 24. But look it’s got negative, so because that’s a positive I need to put negative 12 and negative 12 here. So you cross multiply, cross multiply, negative 12 minus 12 is negative 24 which is the same as that. So therefore x minus 12 times x minus 12 which is x minus 12 squared, all right? So see it’s very very repetitive isn’t it as long as you know what squared is 144, okay?
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