依题意,\(\frac {\Delta y} {\Delta x}=\frac {{{[2(3+\Delta x)-1]}^{2}}-{{5}^{2}}} {\Delta x}=\frac {{{(5+2\cdot \Delta x)}^{2}}-{{5}^{2}}} {\Delta x}=20+4\cdot \Delta x\),
\(y'{{|}_{x=3}}=\mathop{\lim}\limits_{\Delta x\to 0}(20+4\cdot \Delta x)=20\),所以函数\(y = {(2x - 1)^2}\)在\(x = 3\)处的导数是20.