Answer:

x⁴ + 1 + 2x² - y²

Step-by-step explanation:

(a + b)(a - b) = a² - b²

(x² + 1 + y)(x² + 1 - y) = ?

a = x² + 1

b = y

(x² + 1 + y)(x² + 1 - y)

(x² + 1)² - (y)²

x⁴ + 1 + 2x² - y²

Answer:

(x^2+1+y)( x^2+1-y)

x^2(x^2+1-y)+1(x^2+1-y)+y(x^2+1-y)

x^4+x^2-x^2y+x^2+1-y+x^2y+y-y^2

x^4+2x^2-y^2