Question

先合并同类项,再求代数式的值:X^2-2X^2+5-X^2-3

Answer 1

X^2-2X^2+5-X^2-3

=(1-2-1)x^2+2

=-2x^2+2

x=-1/2

原式=-2*(-1/2)^2+2

=-2*1/4+2

=-1/2+2

=3/2