If x = a + 1 and y = a – 1 , then the value of x4 + y4

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x = a +	1	; y = a -	1
	a		a

∴ x² - y² =

a +

a -

= 4a ×

= 4

= 4 [∵ (a + b)² – (a – b)² = 4ab]
∴ x⁴ + y⁴ – 2x²y² = (x² – y²)²
= 4² = 16

If x = a +	1	and y = a –	1	, then the value of x⁴ + y⁴ – 2x²y² is :
	a		a