Question

Select all of the following that are quadratic equations.

3x2 + 5x - 7 = 0
x3 - 2x2 + 1 = 0
2x - 1 = 0
5x2+ 15x = 0
6x - 1 = 4x + 7
x2 - 4x = 4x + 7

Answer 1

all except the 2nd, 3rd, and 5th

Answer 2

`3x^2 + 5x - 7 = 0`,
`5x^2+ 15x = 0` and
`x2 - 4x = 4x + 7` are quadratic equations.

Explanation:

We are required to find the quadratic equations.

Now, as we know,

Quadratic equation is an equation having degree 2 and is of the form
`ax^2+bx+c=0`.

So, according to the options, we see that,

The equations
`x^3 - 2x^2 + 1 = 0`,
`2x - 1 = 0` and
`6x - 1 = 4x + 7` have degree 3, 1 and 1 respectively.

Thus, these equations are not quadratic equations.

Hence, the equations 1, 4 and 6 are quadratic equations.