已知a、b满足等式x=a²+b²+20,y=4(2b-a),则x,y的大小关系是x-y=a²+b²+20-4(2b-a)=a²+4a+b²-8b+20=a²+4a+4+b²-8b+16=(a+2)²+(b-4)²a²+4a+b²-8b+20=a²+4a+4+b²-8b+16请
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![已知a、b满足等式x=a²+b²+20,y=4(2b-a),则x,y的大小关系是x-y=a²+b²+20-4(2b-a)=a²+4a+b²-8b+20=a²+4a+4+b²-8b+16=(a+2)²+(b-4)²a²+4a+b²-8b+20=a²+4a+4+b²-8b+16请](/uploads/image/z/5599152-0-2.jpg?t=%E5%B7%B2%E7%9F%A5a%E3%80%81b%E6%BB%A1%E8%B6%B3%E7%AD%89%E5%BC%8Fx%3Da%26%23178%3B%EF%BC%8Bb%26%23178%3B%EF%BC%8B20%2Cy%EF%BC%9D4%EF%BC%882b-a%EF%BC%89%2C%E5%88%99x%2Cy%E7%9A%84%E5%A4%A7%E5%B0%8F%E5%85%B3%E7%B3%BB%E6%98%AFx-y%3Da%26%23178%3B%2Bb%26%23178%3B%2B20-4%282b-a%29%3Da%26%23178%3B%2B4a%2Bb%26%23178%3B-8b%2B20%3Da%26%23178%3B%2B4a%2B4%2Bb%26%23178%3B-8b%2B16%3D%28a%2B2%29%26%23178%3B%2B%28b-4%29%26%23178%3Ba%26%23178%3B%2B4a%2Bb%26%23178%3B-8b%2B20%3Da%26%23178%3B%2B4a%2B4%2Bb%26%23178%3B-8b%2B16%E8%AF%B7)
已知a、b满足等式x=a²+b²+20,y=4(2b-a),则x,y的大小关系是x-y=a²+b²+20-4(2b-a)=a²+4a+b²-8b+20=a²+4a+4+b²-8b+16=(a+2)²+(b-4)²a²+4a+b²-8b+20=a²+4a+4+b²-8b+16请
已知a、b满足等式x=a²+b²+20,y=4(2b-a),则x,y的大小关系是
x-y
=a²+b²+20-4(2b-a)
=a²+4a+b²-8b+20
=a²+4a+4+b²-8b+16
=(a+2)²+(b-4)²
a²+4a+b²-8b+20
=a²+4a+4+b²-8b+16请详细解释一下这一步
已知a、b满足等式x=a²+b²+20,y=4(2b-a),则x,y的大小关系是x-y=a²+b²+20-4(2b-a)=a²+4a+b²-8b+20=a²+4a+4+b²-8b+16=(a+2)²+(b-4)²a²+4a+b²-8b+20=a²+4a+4+b²-8b+16请
把20拆项20=4+16,再分组配成2个完全平方式
因为(a+2)²≥0,(b-4)²≥0,所以(a+2)²+(b-4)²≥0
所以x-y≥0,即x≥y