Answer:
The quadratic equation is (x + 3)(x + 4) = 5
Step-by-step 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
[tex]x(x^2+1)=0\\x^3+x=0[/tex]
Degree is 3 and hence it is not a quadratic.
Take 2nd equation
[tex]5(4x+2)=3\\20x+10=3[/tex]
Degree is 1 and hence it is not a quadratic.
Finally, we simplify the third equation
[tex](x+3)(x+4)=5[/tex]
Apply FOIL method to simplify the left hand side
[tex]x^2+4x+3x+12=5=5[/tex]
Degree is 2 and hence it is a quadratic equation.
