什么叫控制变量

函数y=log2x(3-x)的定义域是 用一个5个空格的十字框在月历表中框出不同的5个数,这5个数的和最小是几?最大是几? 若xy∈R+,xy^2=4,则x+y的最小值为 普通挂历表某一竖列4个数的和是54,这4个数是? 求这个雨滴素材 雨滴接近地面的过程可以看做匀速直线运动,此时雨滴的速度称为收尾速度.某同学在一本资料上看到,雨滴的收尾速度V与雨滴的半径r成正比,由此该同学对雨滴运动中所受的阻力F作了如下几种 因式分解x的平分-4xy-4+4y的平分 He gets home (at five )in the arternoon(对括号部分提问） I think Tom is at home .(改为否定句） .He does his homework at home.(改为否定句）People usually eat dinner (in the evening).(对括号部分提问）He has breakfast at seve Tom ______(leave)home after a while .But he sometimes _____(leave) home 6 o'clock.还要说明原因 Eevery day Tom went to the market to buy food and other things .Every day Tom went to the market to buy food and other things.He put them in a big basket but he was old and weak,so he always paid another man to carry the basket homefor him.But one Sa (x-32)/16-x/60=5/3 01.x+21-x=16.5, x +0.5×2.16％x－20％×0.5×2.16％x=504.32 怎么解,方程 a+b+c=9.ab+bc+ca=24求b取值范围 what was wrong with him同义句转换 she (is taking a photo of a beautiful girl.）对括号部分提问what was wrong with him同义句转换she (is taking a photo of a beautiful girl.）对括号部分提问 求The girl with the northern soul collection的歌词和翻译 Look for the girl with the broken smile? why?怎么翻译! Who does the girl go there with怎么翻译 I put down a girl of act with dignity最准的翻译 已知实数x、y满足2x-3y=4,并且x≥0,y≤1,则x-y的最大值是?最小值是?） 4（2.5+X）=32.8 这题怎么解? 试判断(x^2-2x-2)(x^2-2x)+9是否有平方根,说明理由 改下列句子中的错误：1 It's time to lunch.2 Is your sister have lunch at home?改下 根据句意和汉语提示完成句子 It isn't the first time for the girl to[ ][ ]{考虑} leaving home. 关于运动和力,下列说法中正确的是其中一个选项是踢出去的足球能在草地上继续运动一段距离,是因为足球具有惯性.这句话不对吗? 15.5÷0.2×x=5怎么解 x÷（32-15）=2.5?方程解 急啊 关于运动和力,下列说法正确的是a 力是使物体保持静止的原因b 力是使物体运动状态改变的原因c 力是维持物体运动的原因d 物体受到力的作用就一定运动 水沸腾后就表示水开了吗?水开了就能喝了吗? 只要沸腾就算水开了? x∧2减4XY减1加4y∧2因式分解 1.汽车沿坡度为1：200的直线从A上坡行驶到B,行程1000m,那么B地比A地高_____m（精确到0.1m）2.在直角三角形ABc中,角C=90度,根据下面条件解直角三角形;（1）b=4根2,tanA=1/4,求a；（2）角A=30度,a+b=3+根3,