3(2x+5y)²-5(x-3y)²

3(2x+5y)²-5(x-3y)² = 12x²+ 75y²-5x²+9y² = 7x² + 84y²

3(2x+5y)²-5(x-3y)²=3(4x²+20xy+25y²)-5(x²-6xy+9y²)=12x²+60xy+75y²-5x²+30xy-45y²=7x²+90xy+30y²

3(2x+5y)²-5(x-3y)² =3(4x²+20xy+25y²)-5(x²-6xy+9y²) =12x²+60xy+75y²-5x²+30xy-45y² =7x²+90xy+30y²