问题
计算题
已知x2﹣2x=2,求代数式(x﹣1)2+(x+3)(x﹣3)+(x﹣3)(x﹣1)的值.
答案
解:(x﹣1)2+(x+3)(x﹣3)+(x﹣3)(x﹣1),
=x2﹣2x+1+x2﹣9+x2﹣4x+3,
=3x2﹣6x﹣5,
=3(x2﹣2x)﹣5,
∵x2﹣2x=2,
∴原式=3 ×2﹣5=1.
已知x2﹣2x=2,求代数式(x﹣1)2+(x+3)(x﹣3)+(x﹣3)(x﹣1)的值.
解:(x﹣1)2+(x+3)(x﹣3)+(x﹣3)(x﹣1),
=x2﹣2x+1+x2﹣9+x2﹣4x+3,
=3x2﹣6x﹣5,
=3(x2﹣2x)﹣5,
∵x2﹣2x=2,
∴原式=3 ×2﹣5=1.