How to clean the dark yellow white sheets?

white sheets can be washed white when they are washed, but it is very important when they are dried. Because sunlight contains a lot of pigment rays, white sheets are easy to absorb sunlight after being soaked in water, so they are easy to get beige, so they can be dried indoors after washing, and then taken to the sun after drying, so they will not change color. Remember to give me a score!