例:已知多项式9-6x-4x^2=7,求2^2+3X=5的值.由9-6x-4x^2=7,移项得-6x-4x ^2=7-9,6x+4x^2=2,
问题描述:
例:已知多项式9-6x-4x^2=7,求2^2+3X=5的值.由9-6x-4x^2=7,移项得-6x-4x ^2=7-9,6x+4x^2=2,
2^2+3x=1,得2x^2+3x+5=6.已知多项式14x+5-21x^2=-2,求6x^2-4x+5的值.
答
14x+5-21x^2=-2 移项得 14x-21x^2=-2-5 3x^2-2x=1 6x^2-4x=2
6x^2-4x+5=2+5=7
也就是6x^2-4x+5=7