# Factorising Quadratic Trinomials using Common Factors and Perfect Squares

## Transcript

Question 25 okay so, what’s the common factor this time guys?

Must be 3, isn’t it? So I’m going to take it out by 3 and make sure guys you’re factorizing properly, make sure you don’t make silly mistakes in this step. So it’s going to be x squared plus 4x plus 4, okay? Now let’s go factorize that. So x and x, now 4 is 2 times 2, isn’t it? So I’m going to put 2 and 2. and I don’t worry about any sign. It’s all going to be positive so x times 2 is 2x that one’s 2x if you add them up you get 4x which is exactly what we have here. So it’s going to be 3, x plus 2, x plus 2.

But guys, how can we simplify further, Remember in our perfect squares?

x plus 2 squared because we’ve got 2 of the kind, so you keep the 3 still out, so you can change the x plus 2 and x plus 2 into x plus 2 squared, all right? So that’s pretty much it. Now guys tell me the common factor, please! Negative 5.

Make sure you take that whole chunk, negative as well. So you change all of these to positive now so it’s positive x squared negative 6 x and positive 9, so make sure you’re switching around all the signs, and let’s go factorize that the middle part got x and x. Now 9, it’s 3 times 3 because that’s a negative I should have a negative 3 and negative 3 because negative 3 times negative 3 is also positive 9. Cross, cross, add them, so negative 3 minus 3 is negative 6x which is exactly same as that one. So negative 5 times x minus 3, x minus 3 which is how can we simplify that further? x minus 3 squared, okay? So don’t forget that last step, teachers will mark you down if you don’t simplify further, alright? So be careful!

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