L1 and L2 are two straight lines. The origin of the coordinate axes is O. L1 has equation 5x + 10y = 8 L2 is perpendicular to L1 and passes through the point with coordinates (8, 6) L2 crosses the x-axis at the point A. L2 intersects the straight line with equation x = –3 at the point B. Find the area of triangle AOB. Show your working clearly.

Respuesta :

Answer:

40 sq units

Step-by-step explanation:

[tex]5x + 10y = 8\\\Rightarrow y=\dfrac{8-5x}{10}\\\Rightarrow y=-\dfrac{1}{2}x+\dfrac{2}{5}[/tex]

Slope of [tex]L_2[/tex] is [tex]m_2[/tex]

[tex]m_1m_2=-1\\\Rightarrow m_2=-\dfrac{1}{m_1}\\\Rightarrow m_2=-\dfrac{1}{-\dfrac{1}{2}}\\\Rightarrow m_2=2[/tex]

[tex]L_2[/tex] passes through point [tex](8,6)[/tex]

[tex]y-6=2(x-8)\\\Rightarrow y=2x-16+6\\\Rightarrow y=2x-10[/tex]

Point at x axis where [tex]L_2[/tex] intersects is

[tex]0=2x-10\\\Rightarrow x=\dfrac{10}{2}\\\Rightarrow x=5[/tex]

Point [tex]A[/tex] of the triangle will be [tex](5,0)[/tex]

[tex]L_2[/tex] intersects line [tex]x=-3[/tex]. The point is

[tex]y=2\times(-3)-10\\\Rightarrow y=-6-10\\\Rightarrow y=-16[/tex]

The points of the triangle are [tex]A(5,0), O(0,0), B(-3,-16)[/tex]

Area of triangle is given by

[tex]A=\dfrac{|A_x(B_y-O_y)+B_x(A_y-O_y)+O_x(A_y-B_y)|}{2}\\\Rightarrow A=\dfrac{|5(-16-0)+-3(0-0)+0(0-(-16))|}{2}\\\Rightarrow A=40\ \text{sq units}[/tex]

The area of the triangle is 40 sq units.

Ver imagen boffeemadrid