Trapezium

The lengths of parallel sides of a trapezium are (2x+3) and (x+8), and the distance between them is (x+4). If the area of the trapezium is 590, find the value of x.

Correct answer:

x =  -23.6667

Step-by-step explanation:

$$\begin{gathered} S=590 \\ a=2x+3 \\ c=x+8 \\ h=x+4 \\ S=\frac{a+c}{2}\cdot h \\ 590=((2x+3)+(x+8))/2\cdot (x+4) \\ 590=((2x+3)+(x+8))/2\cdot (x+4) \\ -1.5x^2-11.5x+568=0 \\ 1.5x^2+11.5x-568=0 \\ a=1.5;b=11.5;c=-568 \\ D=b^2-4ac=11.5^2-4\cdot 1.5\cdot (-568)=3540.25 \\ D>0 \\ {x}_{1,2}=\frac{-b\pm \sqrt{D}}{2a}=\frac{-11.5\pm \sqrt{3540.25}}{3} \\ {x}_{1,2}=-3.833333\pm 19.833333 \\ {x}_1=16 \\ {x}_2=-23.666666667 \\ x>0 \\ x=x_2=(-23.6667)=-\frac{71}{3}=-23\frac{2}{3}\doteq -23.6667 \\ a=2\cdot x+3=2\cdot (-23.6667)+3=-\frac{133}{3}=-44\frac{1}{3}\doteq -44.3333 \\ c=x+8=(-23.6667)+8=-\frac{47}{3}=-15\frac{2}{3}\doteq -15.6667 \\ h=x+4=(-23.6667)+4=-\frac{59}{3}=-19\frac{2}{3}\doteq -19.6667 \\ {S}_2=\frac{a+c}{2}\cdot h=\frac{(-44.3333)+(-15.6667)}{2}\cdot (-19.6667)=590 \end{gathered}$$

Our quadratic equation calculator calculates it.

Try another example