Question

what is the area of △ghi? area = square units

Explanation:

Step1: Determine base and height

From the graph, for $\triangle GHI$, the base $HI$ is the horizontal distance between $H$ and $I$. The $y -$coordinate of $H$ and $I$ is 4. The $x -$coordinate of $H$ is - 9 and of $I$ is 9. So the length of the base $HI=9 - (-9)=18$. The height is the vertical distance from $G$ to the line $HI$. The $y -$coordinate of $G$ is - 1 and of $H$ (and $I$) is 4. So the height $h = 4-(-1)=5$.

Step2: Apply area formula

The area formula for a triangle is $A=\frac{1}{2}\times base\times height$. Substitute base = 18 and height = 5 into the formula: $A=\frac{1}{2}\times18\times5$.
$A = 45$.

Answer:

45