Factorising Quadratic Trinomials using Positive Common Factors
Transcript
Okay! First of all guys, can you guys tell me what the common factor is that I can take out? So see at the moment, it’s not monic, it’s got two in front and you can see that two is a common factor. So I’m going to first take 2 out and use brackets.
So here I’ll just have x square here 5x and 6. Yeah! So keep that 2 out and now I’m just going to try to see if I can factorize the middle part. So you get your x and x, 6 is 1 and 6, 2 and 3. So I’m going to use 2 and 3 because 2 plus 3 makes 5, okay? So it’s going to be 2x 3x 5x which is the same as that so I’m pretty sure I’ve got the right choices.
So you keep your 2 out and you put x plus 2 times x plus 3 on the right-hand side, okay? So pretty much this part is this part factorized and you just stick the two in front that’s the only the difference, so how easy is that.
23! Okay! What’s the common factor? Easy peasy! Three. So we’ll have this left inside so let’s try factorizing the middle part x and x, now three, we’ve got negative three here so we need to have one positive and one negative, don’t we?
I’m going to use positive 1 minus 3 because I know that 1 minus 3 is negative 2. So let’s just check that x that’s negative 3x and I know that x minus 3x is negative 2x which is what we’ve got here that’s correct. So we keep our three outside and we’ve got x plus one, x minus three, all right?
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