因为,(2x²-4x+21)-(2y-y²) = 2(x-1)²+(y-1)²+18 ≥ 18 > 0 ,
所以,2x²-4x+21 > 2y-y² .
已知x,y∈R,求证：2x²-4x+21>2y-y².
1个回答
相关问题
-
已知x.y属于R.求证,(x²+y²)/2≥【(x+y)/2】²
-
已知x,y∈R,求证x2-xy+y2>=x+y-1
-
已知x,y∈R,求证:x^2+y^2≥xy+x+y-1
-
已知x.y∈R,求证x2+y2+1≥x+y+xy
-
已知x,y∈R,满足（x²+y²+2)(x²+y²-1)-18≤0.求证：xy≤
-
(1)已知实数x,y,z满足x=6-y,z^2=xy-9,求证:x=y (2)已知x^2+x-1=0,求代数式21x^4
-
已知x＞y,求证x³-y³＞2x²y-2xy²
-
已知x＞y,求证:x³－y³＞2x²y－2xy²
-
已知x,y∈R,求证:x-xy+y≥x+y-1
-
已知x,y∈R,求证:x+y+1≥x+y+xy