>>629
(1)(右辺)^2−(左辺)^2≧0
(2)(右辺) - (左辺) = (1/4)(|x|-2)^4
(3) |1/(x^2+4)-1/(y^2+4)|
=|(y^2-x^2)/{(x^2+4)(y^2+4)}|
≦|x+y| * {1/(x^2+4)} * {1/(y^2+4)} * |x-y|
≦(|x|+|y|) * {1/(x^2+4)} * {1/(y^2+4)} * |x-y|
≦{(1/4)(x^2+4)} + (1/4)(y^2+4)} * {1/(x^2+4)} * {1/(y^2+4)} * |x-y|
= (1/4){1/(x^2+4)} + 1/(y^2+4)} * |x-y|
≦(1/4){(1/4)+(1/4)} * |x-y|
= (1/8)|x-y|