Answer:
5
Step-by-step explanation:
[tex] \because {(x + y)}^{2} = {x}^{2} + {y}^{2} + 2xy \\ \therefore \: {(5)}^{2} = {x}^{2} + {y}^{2} + 2 \times 10 \\ \therefore \: 25 = {x}^{2} + {y}^{2} + 20 \\ \therefore \: 25 - 20 = {x}^{2} + {y}^{2} \\ \huge \red{ \boxed{ \therefore \: {x}^{2} + {y}^{2} = 5}}[/tex]
