Which of the following are quadratic equations?
$3x^2\ –\ 5x\ +\ 9\ =\ x^2\ –\ 7x\ +\ 3$

Given:

Given equation is $3x^2\ –\ 5x\ +\ 9\ =\ x^2\ –\ 7x\ +\ 3$.

To do:

We have to check whether the given equation is quadratic.

Solution:

The standard form of a quadratic equation is $ax^2+bx+c=0$.

$3x^2\ –\ 5x\ +\ 9\ =\ x^2\ –\ 7x\ +\ 3$

$3x^2-x^2-5x+7x+9-3=0$

$2x^2+2x+6=0$

$2x^2+2x+6=0$ is of the form $ax^2+bx+c=0$ where $a=2, b=2$ and $c=6$.

Therefore, $3x^2\ –\ 5x\ +\ 9\ =\ x^2\ –\ 7x\ +\ 3$ is a quadratic equation.