Solve the inequality (x-4)(3-x)>0

题目

Solve the inequality (x-4)(3-x)>0
find the set of values of x for which 2x2+3x+2大于或等于4
Rewrite 3x2+9x+2 as a(x+p)2次平方+q by completing the square and hence.sketch the curve y=3x2+9x+2 stating clearly the co-ordinates of the turning point and y_ intercept.
没人看得懂吗?第一题就是 不等式 (x-4)(3-x)>0
第二题就找出值 2x2+3x+2大于或等于4
第三题就算了,只是不敢确定
答案我知道是 X＞4或X＜3

答案

记住口诀!小于取中间,大于取两边!第一题：(x-4)(3-x)>0.首先,使不等式左边未知数系数化为正数,即 (x-4)(x－3)＜0.3＜X＜4
第二题：2x2+3x+2大于或等于4.即4＋3X＋2≥4.X≥－2／3