(x² - (1/5x²))²
Using (a-b)² = a²-2×ab+b²
(x²)² -2x²×(1/5x)² + (1/5x²)²
x⁴ -2x⁴ + 1/25⁴
We developed the fraction to obtain the lowest common denominator
x⁴/1 - 2x⁴/5 +x⁴/25
25×(X⁴)/25×1 - 5×(2x⁴)/5×5 + x⁴/25
25×⁴/25 - 10x⁴/25 + x⁴/25
{25×⁴- 10x⁴ + 1x⁴}/25
{26×⁴- 10x⁴}/25
{26×⁴- 10x⁴}/25
16x⁴/25