The condition is x 2+(x+y) 2.

The sum formula 2 is (n+ 1)[x+(3y/2)], and the inequality (excluding cosine of included angle) is obtained by using the vector inner product formula:

2[x+(3y/2)]=[3(x+y)-x]=[ vector (x+y, x)] inner product] [vector (3,-1)]

& lt=[ root number (x 2+(x+y) 2)]] [root number (3 2+(-1) 2)] = a (root number 10)

When x=-3(x+y), we get the equal sign, that is, 2x=-3y, that is, a_ 1=-(3/2)nd.

Therefore, the maximum value of Formula 2 is (n+ 1)a (root number 10)/2.