X²-xy+y²=(x+y)²-3xy=4*3-3=9
已知x=根号下2-根号下3,y=根号下2+根号下3,求x的平方-xy+y的平方x² - xy + y²= (x + y)² - 3xy= (√2 - √3 + √2 + √3)² - 3(√2 - √3)(√2 + √3)= (2√2)² - 3×(-1)= 8 + 3= 11
