若x+y=9且xy=16,求x2+y2.
问题描述:
若x+y=9且xy=16,求x2+y2.
答
x2+y2=(x+y)2-2xy,
=92-2×16,
=49.
若x+y=9且xy=16,求x2+y2.
x2+y2=(x+y)2-2xy,
=92-2×16,
=49.