Question

What was Dimitri's mistake? He mixed up the coordinates of the ordered pair when Substituting it into the equations 7x+9y=-4 and 5x-2y=6

Answer 1

Answer:

He made a mistake in his calculations when simplifying 5x - 2y

Step-by-step explanation:

Given

The coordinate pair

$(x,y) = (2,-2)$

The equations

$7x + 9y = ?$

$5x - 2y = ?$

Dimitri's Solution

$Equation\ 1: 7x + 9y = -4.$

$7(2) + 9 (-2) = -4.$

$14 + (-18) = -4.$

$-4 = -4.$

$Equation\ 2: 5x -2y = 6.$

$5(2) - 2 (-2) = 6.$

$10 - 4 = 6.$

$6 = 6.$

Required

Identify Dimitri’s mistake

In the first equation, Dimitri made no mistake.

However, he made a mistake when simplifying the second equation.

We have:

$5x - 2y$

and

$(x,y) = (2,-2)$

Substitute $x = 2$ and $y = -2$

So, we have:

$5(2) -2(-2)$

Open bracket

$10 +4$

Finally, we have:

$14$