Question

Use matrices to determine the coordinates of the vertices of the reflected figure. Triangle GHI with vertices G(-1,7) H(8,1) I(4,-5) reflected over the y-axis

Answer 1

G'(1,7), H'(-8,1), I'(-4,-5)

Explanation:

right answer on edge2020

Answer 2

G'(1,7), H'(-8,1), I'(-4,-5)

Explanation:

The transformation matrix for reflection across the y-axis is an identity matrix with the x-multiplier negated:

`\left[\begin{array}{cc}-1&0\\0&1\end{array}\right]`

Multiplying the coordinates by this gives ...

`\left[\begin{array}{cc}-1&0\\0&1\end{array}\right]\cdot\left[\begin{array}{ccc}-1&8&4\\7&1&-5\end{array}\right]=\left[\begin{array}{ccc}1&-8&-4\\7&1&-5\end{array}\right]`

That is, the reflected points are G'(1,7), H'(-8,1), I'(-4,-5).