Question

Which of the following equations is quadratic?

x(x2 + 1) = 0
5(4x + 2) = 3
(x + 3)(x + 4) = 5

Answer 1

(X + 3)( x + 4) = 5 is the correct answer

Answer 2

The quadratic equation is (x + 3)(x + 4) = 5

Explanation:

If the degree of a polynomial is two then the polynomial is known as a quadratic.

Now, in the given equations we see which polynomial has a degree 2.

Simplify the first equation

`x(x^2+1)=0\\x^3+x=0`

Degree is 3 and hence it is not a quadratic.

Take 2nd equation

`5(4x+2)=3\\20x+10=3`

Degree is 1 and hence it is not a quadratic.

Finally, we simplify the third equation

`(x+3)(x+4)=5`

Apply FOIL method to simplify the left hand side

`x^2+4x+3x+12=5=5`

Degree is 2 and hence it is a quadratic equation.