Answer:
x²+10xy+25y²
Step-by-step explanation:
(x+5y)²=(x+5y)(x+5y)=x×x+5y×x+x×5y+5y×5y=x²+5xy+5xy+25y²=x²+10xy+25y²
But it can be much easier
(a+b)²=a²+2ab+b²
