Answers

2014-09-02T00:43:54+08:00
2t ^2 + 11t +12 < 0 \\ \\first\ we \ solve: \\2t ^2 + 11t +12 =0 \\ (t+ 4) (2t +3)=0 \\t+4=0 \ \ or \ \2t+3=0 \\t=-4\ \ or \ \ 2t= -3 \\ x=-5\ \ or \ \ t= -\frac{3}{2}=-1.5

 So   we  know   that the curve is u-shaped and   it crosses the t-axis at t=-5 and t= - 1.5 5

The curve is less than zero  :

-4 < t < - 1.5



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