Glucose must be remembered, C6H 12O6. Do you remember that sugar was once called "carbohydrate" and glucose is a six-carbon sugar, so it is (CH2O)6, that is, C6H 12O6. (Limited to memory, actually the structure of glucose is not (CH2O)6)

Sucrose is disaccharide, which is obtained by removing 1 molecular water from glucose and fructose. Fructose and glucose have the same molecular formula and are isomers, so sucrose = glucose+fructose-water = c6h12o6+c6h12o6-H2O = c12h22o1.

Starch is a macromolecular substance composed of many glucose. Starch can be regarded as the dehydration connection between glucose molecules, but only 1 water molecule is removed from one glucose, so the molecular formula of starch is = (glucose-water) × n = (c6h12o6-H2O) × n = (c6h10o5) n.