# Thread: Is this a perfect-square trinominal?

1. ## Is this a perfect-square trinominal?

Problem is 27x^2-117x-90

So should I take the GCF of 9 out first?

9(3x^2-13x-10)

Or do I look at the problem before that and see if it is a perfect-square?

Thanks

2. ## Re: Is this a perfect-square trinominal?

when I work it out i get 9(3x+2)(x-5)

3. ## Re: Is this a perfect-square trinominal?

Originally Posted by bashemgud
Problem is 27x^2-117x-90
The $\displaystyle {\bf\color{red}-}90$ tells you it is not a square trinominal.

4. ## Re: Is this a perfect-square trinominal?

Originally Posted by Plato
The $\displaystyle {\bf\color{red}-}90$ tells you it is not a square trinominal.

can you tell me why?

5. ## Re: Is this a perfect-square trinominal?

Originally Posted by moonwoo
can you tell me why?
The constant term in a perfect square is always positive. Expand $\displaystyle (a+b)^2$ and note the sign of b^2

6. ## Re: Is this a perfect-square trinominal?

Originally Posted by bashemgud
when I work it out i get 9(3x+2)(x-5)
This is correct. Clearly this is not a perfect square...