7.设f(2x-1)=(ln x)/(sqrt(x))，求int_(1)^7f(x)dx.

令 $x = 2t - 1$，则 $dx = 2dt$，当 $x = 1$ 时，$t = 1$；当 $x = 7$ 时，$t = 4$。代入得
$\int_{1}^{7} f(x) \, dx = 2 \int_{1}^{4} f(2t-1) \, dt = 2 \int_{1}^{4} \frac{\ln t}{\sqrt{t}} \, dt.$
使用分部积分法，设 $u = \ln t$，$dv = \frac{1}{\sqrt{t}} \, dt$，则 $du = \frac{1}{t} \, dt$，$v = 2\sqrt{t}$。
$\int \frac{\ln t}{\sqrt{t}} \, dt = 2\sqrt{t} \ln t - 4\sqrt{t},$
计算得
$\int_{1}^{4} \frac{\ln t}{\sqrt{t}} \, dt = (4\ln 4 - 8) - (0 - 4) = 4\ln 4 - 4 = 8\ln 2 - 4.$
因此，
$2 \int_{1}^{4} \frac{\ln t}{\sqrt{t}} \, dt = 2(8\ln 2 - 4) = 16\ln 2 - 8.$
答案： $\boxed{16\ln 2 - 8}$