题目
If the function g is such that g(x) = g(x– 1) – x + 2 and g(2) = 2, what is the value of g(5)?
解析
如果函数\(g\)满足\(g(x)=g(x - 1)-x + 2\)且\(g(2)=2\),那么\(g(5)\)的值是多少?
- 已知\(g(2)=2\),根据函数关系\(g(x)=g(x - 1)-x + 2\)来依次求出\(g(3)\)、\(g(4)\)和\(g(5)\)的值。
1. **求\(g(3)\)的值:**
当\(x = 3\)时,\(g(3)=g(3-1)-3 + 2=g(2)-3 + 2\),因为\(g(2)=2\),所以\(g(3)=2-3 + 2=1\)
2. **求\(g(4)\)的值:**
当\(x=4\)时,\(g(4)=g(4 - 1)-4+2=g(3)-4 + 2\),由\(g(3)=1\)可得\(g(4)=1-4 + 2=-1\)
3. **求\(g(5)\)的值:**
当\(x = 5\)时,\(g(5)=g(5-1)-5+2=g(4)-5 + 2\),因为\(g(4)=-1\),所以\(g(5)=-1-5+2=-4\)
综上,答案是E选项。