Question

1.已知x=1/2(根号5+根号3）,y=1/2（根号5-根号3）,求x平方+6xy+y平方的值

Answer 1

1.x^2+6xy+y^2(^2就是平方)

=(x+y)^2+4xy

x+y=1/2(根号5+根号3）+1/2（根号5-根号3）=根号5

xy=1/2(根号5+根号3）*1/2（根号5-根号3）=1/4(5-3)=1/4*2=1/2

则原式=(根号5)^2+4*1/2

=5+2=7