9-6y-4y∧2,求2y^2+3y+7的值,解由9-6y-4y^2=7得-6y-4y^2=7-9即6y+4y^=2,所以2y^2+3y=1所以2y^2+3y+7=8
已知14X+5-21x^2的值是-2,求6X^2-4x+5