ag-gipp/GoUldI

<math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mfenced close=")" open="("><mrow><mi>x</mi><mo>-</mo><mi>y</mi></mrow></mfenced><mn>2</mn></msup><mi>U</mi><mo>=</mo><msup><mfenced close=")" open="("><mrow><msqrt><mrow><msup><mi>x</mi><mn>4</mn></msup><mo>+</mo><msup><mi>a</mi><mn>4</mn></msup></mrow></msqrt><mo>+</mo><msqrt><mrow><msup><mi>y</mi><mn>4</mn></msup><mo>+</mo><msup><mi>a</mi><mn>4</mn></msup></mrow></msqrt></mrow></mfenced><mn>2</mn></msup><mo>-</mo><msup><mfenced close=")" open="("><mrow><msup><mi>x</mi><mn>2</mn></msup><mo>-</mo><msup><mi>y</mi><mn>2</mn></msup></mrow></mfenced><mn>2</mn></msup></math>