小万有7支铅笔,给了小红4只,小万还剩____支铅笔。
已知点P是椭圆x2+4y2=4上的任意一点,A(4,0),若M为线段PA中点,则点M的轨迹方程是( )
One way ____ (solve) this problem is ____ (plan) your time more carefully.