Define $L:=\int_{0}^{1}\sqrt{(x'(t))^2+(y'(t))^2} dt$.
Show $L\geq|x(1)-x(0)|$.
I don't know where to start.
Hint: $$\int_{0}^{1}\sqrt{(x'(t))^2+(y'(t))^2} dt \ge \int_{0}^{1}\sqrt{(x'(t))^2} dt = \int_{0}^{1} \lvert x'(t) \rvert dt $$
What happens if you replace the $y'(t)$ term by $0?$
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Hint: $$\int_{0}^{1}\sqrt{(x'(t))^2+(y'(t))^2} dt \ge \int_{0}^{1}\sqrt{(x'(t))^2} dt = \int_{0}^{1} \lvert x'(t) \rvert dt $$