Question

若多项式x的平方-2x+3=5,则多项式-x的平方+2x+3=?,3x的平方-6x-1

Answer 1

解

x²-2x+3=5

x²-2x=2

-x²+2x+3

=-(x²-2x)+3

=-2+3

=1

3x²-6x-1

=3(x²-2x)-1

=3×2-1

=5

3a²-2b-1=7

3a²-2b=8

两边除以3,得：

a²-2/3b=8/3

∴a²-2/3b+3

=8/3+3

=17/3