已知|a-b|=5,求2（a-b）的平方-2a+2b-1的值.

解
/a-b/=5
∴a-b=5
或a-b=-5
当a-b=5时
2(a-b)²-2a+2b-1
=2(a-b)²-2(a-b)-1
=2×5²-2×5-1
=50-10-1
=39
当a-b=-5时
2(a-b)²-2a+2b-1
=2(a-b)²-2(a-b)-1
=2×(-5)²-2×(-5)-1
=50+10-1
=59