《invisible war》的歌詞如下：
Verse 1：
The war is invisible
It’s all around us
In the air we breathe
In the things we buy
Chorus：
But we don’t see it
We don’t feel it
It’s a war that’s fought
In our minds and hearts
Verse 2：
The bombs are silent
No sound is heard
Except the ones inside
That we can’t ignore
Chorus：
But we don’t see it
We don’t feel it
It’s a war that’s fought
In our minds and hearts
Bridge：
We must stand up
And speak out loud
This is a war
That we cannot lose
Chorus：
We must see it now
We must feel it too
This is a war
That we must win
Outro：
The war is invisible
But it’s real已知函式f(x) = x^3 - 3x^2 + 9x - 2在區間[a,b]上的值域為[a,b]，求a和b的值。
解：因為$f(x) = x^{3} - 3x^{2} + 9x - 2$，所以$f^{\prime}(x) = 3x^{2} - 6x + 9$，令$f^{\prime}(x) = 0$，得$x = 1$或$x = 3$，當$x \in ( - \infty,1)$時，$f^{\prime}(x) < 0$，函式單調遞減；當$x \in (1,3)$時，$f^{\prime}(x) > 0$，函式單調遞增；當$x \in (3, + \infty)$時，$f^{\prime}(x) < 0$，函式單調遞減．所以當$x = 1$時，函式取得極小值$- 2$；當$x = 3$時，函式取得極大值$9$.因為函式在區間$\lbrack a,b\rbrack$上的值域為$\lbrack a,b\rbrack $，所以$a = - 2,b = 9$.所以實數a的值為$- 2$，實數b的值為$9$.