Question

Which of the following equations is quadratic?

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

Answer 1

I think it's 2 because the quadratic equation looks like this ax^2+bx+c=0 and option 2 looks like it.

Explanation:

For option 1: x(x^2+1)=0

x^3+1=0 ( This also does not look like the quadratic function, so it couldn't be the answer)

For option 2: (x+3)(x+4)=5

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

x^2+6x+12=5 ( This does look like the quadratic function, so it could be the answer)

For option 3:

5(4x+2)=3

20x+10=3 ( This also does not look like the quadratic function, so it couldn't be the answer)

Answer 2

the first one

x(x2 + 1)= 0