Question

a的平方-3ab+9b的平方,其中a=-2,b=三分之二的值是 还有2（x-y）-3（y-x）,其中x-y=-1

Answer 1

解

a²-3ab+9b²

=(-2)²-3×(-2)×(2/3)+9×(2/3)²

=4+4+4

=12

2(x-y)-3(y-x)

=2(x-y)+3(x-y)

=5(x-y)

=5×(-1)

=-5