(a + 1)(a - 1)

(a - 1)(a - 1)

(a + 1)(a + 1)

1

(x + 4)(x + 5)

(x + 20)(x + 1)

(x - 11)(x + 11)

$$\left(x-11\right)^2$$

$$(x+16)(x+2)$$  

$$(x-16)(x-2)$$  

$$\left(x+6\right)\left(x+3\right)$$  

$$\left(x-3\right)\left(x-6\right)$$  

$$\left(x+9\right)\left(x-2\right)$$  

$$\left(x-9\right)\left(x+2\right)$$  

$$\left(x+6\right)\left(x-3\right)$$  

$$\left(x-6\right)\left(x+3\right)$$  

$$\left(x-2\right)\left(x-3\right)$$  

$$\left(x+2\right)\left(x+3\right)$$  

$$\left(x+1\right)\left(x-6\right)$$  

$$\left(x+6\right)\left(x-1\right)$$  

$$\left(x-8\right)\left(x+5\right)$$  

$$\left(8-x\right)\left(x+5\right)$$  

$$\left(8-x\right)\left(5-x\right)$$  

$$\left(x+8\right)\left(x-5\right)$$  

$$\left(x-3\right)\left(5x-1\right)$$  

$$\left(x+1\right)\left(5x+3\right)$$  

undefined 

$$\left(x+3\right)\left(5x-1\right)$$  

$$\left(2x-1\right)\left(7x-1\right)$$  

$$\left(2x+1\right)\left(7x+1\right)$$  

$$\left(2x+1\right)\left(7x-1\right)$$  

$$\left(2x-1\right)\left(7x+1\right)$$  

$$\left(2x+3\right)\left(3x-1\right)$$  

$$\left(2x+3\right)\left(3x+1\right)$$  

$$\left(2x+1\right)\left(3x-3\right)$$  

$$\left(2x-3\right)\left(3x-1\right)$$  

$$\left(3s-5\right)\left(3s+5\right)$$  

$$\left(3s-5\right)\left(3s-5\right)$$  

$$\left(3s+5\right)\left(3s+5\right)$$