Question

已知A=x的2次方+y的2次方+xy,B=3x-x的2次方,当x=3分之2,y=2分之1时,求2A-B的值?

Answer 1

2A-B=2x²+2y²+2xy-3x+x²=3x²+2y²+2xy-3x;

带入x=3分之2,y=2分之1；

=3*4/9+2/4+2/3-3*2/3;

=4/3+1/2+2/3-2;

=2+1/2-2;

=1/2;