( x³ - 4)

( x² - 3)

( x² + 4)

( x² - 4)

Because 4 is not a perfect cubed number.

Because 4 is not a perfect squared number.

Because 49 is not a perfect squared number.

Because we can't factor using difference of two squares if it is addition sign.

3( x + 5 ) ( x - 5 )

Does not factor (prime)

( x + 5 ) ( x - 5 )

3( x - 5 ) ( x - 5 )

$$x^2-81$$  

$$x^2+9$$  

$$2x^2-49$$  

$$x^2-1$$  

$$36x^2-25$$  

$$x^2-6x+9$$  

$$x^2+10x+25$$  

$$x^2+12x-36$$  

$$4x^2-20x+25$$  

$$9x^2-16x+100$$  

$$\left(4y+3\right)\left(4y-3\right)$$  

$$\left(8y\ +\ 3\right)^2$$  

$$\left(8y-3\right)^2$$  

$$\left(4y-3\right)^2$$  

$$\left(a-5\right)\left(a+5\right)$$  

$$\left(a+5\right)^2$$  

$$\left(a-5\right)^2$$  

$$\left(a-10\right)^2$$  

$$\left(8x-7\right)\left(8x+7\right)$$  

$$\left(8x-7\right)^2$$  

$$\left(16x+7\right)^2$$  

$$\left(8x+7\right)^2$$  

(x + 12)²

(x + 9)²

(x + 15)²

(x + 13)²

2(2x + 9)²

(2x + 9)²

(2x + 9)(2x - 9)

(2x - 9)²