x²+y²=(x+y)²-2xy=2²-2×(-15)=34(y+1)/(x+1)+(x+1)/(y+1)通分得=[(y+1)²+(x+1)²]/[(x+1)(y+1)]展开得=[y²+2y+1+x²+2x+1]/(xy+x+y+1)=[(x²+y²)+2(x+y)+2]/[xy+(x...