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Find the area of the triangle whose vertices are (–8, 4), (–6, 6) and (–3, 9).

Solution:

The provided vertices are:

$({{x}_{1}},\text{ }{{y}_{1}})\text{ }=\text{ }\left( -8,\text{ }4 \right)$

$({{x}_{2}},\text{ }{{y}_{2}})\text{ }=\text{ }\left( -6,\text{ }6 \right)$

$({{x}_{3}},\text{ }{{y}_{3}})\text{ }=\text{ }\left( -3,\text{ }9 \right)$

The area of triangle $=\text{ }\left( 1/{{}_{2}} \right)\text{ }({{x}_{1}}({{y}_{2}}-{{y}_{3}})\text{ }+\text{ }{{x}_{2}}({{y}_{3}}-{{y}_{1}})\text{ }+\text{ }{{x}_{3}}({{y}_{1}}-{{y}_{2}}))$

$=\text{ }\left( {\scriptscriptstyle 1\!/\!{ }_2} \right)\text{ }\left( -8\left( 6\text{ }\text{ }9 \right)\text{ }+\text{ }-6\left( 9\text{ }\text{ }4 \right)\text{ }+\text{ }-3\left( 4\text{ }\text{ }6 \right) \right)$

$=\text{ }\left( {\scriptscriptstyle 1\!/\!{ }_2} \right)\text{ }\left( -8\left( -3 \right)\text{ }+\text{ }-6\left( 5 \right)\text{ }+\text{ }-3\left( -2 \right) \right)$

$=\text{ }\left( {\scriptscriptstyle 1\!/\!{ }_2} \right)\text{ }\left( 24\text{ }\text{ }30\text{ }+\text{ }6 \right)$

$=\text{ }\left( {\scriptscriptstyle 1\!/\!{ }_2} \right)\text{ }\left( 30\text{ }\text{ }30 \right)$

$=\text{ }0\text{ }units$.