c++求实数的绝对值

为什么估算出来的电能,电能表计算出来的电能和从电费单得知的电能使用量会不同?如题. [(X+Y)平方-(X-Y)平方]÷(2XY),其中X=10 Y=5 电表如何计算电费另：我有一朋友从我处分接线，他也使用三相电，电表也是三相四线电表，但没有接互感器。那么他的电表用电量是否要剩40倍。注：我的电表参数是DT862-4型 三相四线有功 一元二次不等式组-4 智能电能表可以直接计算出电费吗?智能电能表有复费率功能,那么它可以直接计算出用户所用的电费吗?如果是复费率,可以通过它上面的485接口读出费率是多少吗?回答满意再加30分. 已知x-y=2,求x平方-2xy+y平方 x平方+6xy=16,y平方-4xy=-12,则x平方+2xy+y平方的值为 -a³-（3a²＋7a-5）-（a³-7a＋4） 若a=x平方-2xy+y平方,b=x平方+2xy+y平方,则4xy可表示为______ 已知 a²-3a+1=0,求 3a﹙³﹢¹﹚-7a³-3a²+a／a²+1的值 x的平方-2xy+y的平方=（ ）-4xy M=x的平方-2xy+y的平方,N=x的平方+2xy+y的平方,则4xy等于? 当x=2007,y=2008时,求x^4-y^4/x^2-2xy-y^2÷x^2+y^2/y-x=分式的计算 出租屋电费最高收费是多少,现在有房东既然收1.5元一度的电费,是不是小榄电费一下就涨这么多了呢 已知x－y=2,那x²－2xy+4＋y²＝? 电费又升价了~而家出租屋收几钱度? 已知2x^2+4x+y^2=2xy-4,求x,y的值 2011年北京海淀高三数学一模理答案 She very likes Chinese food怎么错了 How can I tell you that I love you more than life.的中文意思 Sally likes Chinese food very much,_____Fujian food,Guangdong food,Sichuan food.A.with B.such as C.for She likes eating food very much, especially (particularly) banana.banana or bananas? 谁知道tell me hao can i tell you that i love you more than life的歌名是什么? Cathy likes ( ) food.She loves cookies,chocolate,jelly and pudding very much.She( )ice-cream after dinner every day.TOO much sweet dood makes her fat .Cathy has go on a ( ) .Her doctor tells her that she must eat ( )of vegetables and fruit .Cathy sho 求歌名：baby ,tell me how can I tell you that i love you more than life出自哪一首如题 电表电费怎么算我刚搬进去电表原度数（黑色172 红色4） 过了半个月现在是度数是（黑色180 红色8）到底我要交多少电费? 4个1相乘等于多少 The baby was very happy when he saw his mother.同意句The baby was very happy （ ） saw his mothe 三项电表电费怎么算我们有个三项四线的电表是对外出租的,我们每个月收电费是按表上的数字算,表上的系数是 3*380/220V 3*15(60)A 50Hz. the baby likes milk very much ,very much能用什么代替 the baby feels (safe) when his mother hold himin her arm Baby teii me how can I show you That I love you more than life