x^2+9=(10-x)^2
x^2+9=x^2-20x+100
20x=100-9
20x=91
x==4.55x^2-20x+100这里是什么(10-x)^2=x^2-20x+100x^2-20x+100这里不是应该是 10^2-20x+100吗(10-x)^2=(x-10)^2=x^2-20x+100