How to show that the spectrum is equal to the range of $y$

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How to show that the spectrum of $T_y$ is equal to the range of $y$

Given $y\in C[0,1]$ and $T_y: C[0,1] \rightarrow C[0,1]: x\mapsto x\cdot y$

Any help is appreciated, thanks.

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Here's a hint:

$$u\mapsto (\lambda - T_y)u = \lambda u - y u = (\lambda - y)u$$

is invertible for which $\lambda$?