Question

Which of the following is not a quardraic 'equation? 1 x^2 +4x =11 + x^2 .2 x^2=4x ,3 5x^2 = 90 , 2x -x^2 = x^2=x^ + 5

Answer 1

Step-by-step explanation:

A quadratic equation must be in a form

$a {x}^{2} +bx \: + c \: = 0$

lets check one by one all options and see which one fits.

a) x^2 +4x = 11 + x^2

=> 4x = 11

=> 4x-11 = 0

This is a linear equation. There is no x^2 in last step.

* most student just see a x^2 and hrridly qualify it as quadratic. but you must not hurry and analyse it to the last.

b) x^2=4x

=> x = 4

=> x-4 = 0

This is not quadratic equation. It is a linear equation.

c) 5x^2 = 90

=> 5x^2 - 90 = 0

=> x^2 - 18 = 0

This is a quadratic equation. In the last step there is x^2. You can make it all the coefficients.

a=1 , b=0 , c=(-18)

d) 2x -x^2 = x^2 + 5

=> -2x^2 + 2x - 5 = 0

This is a quadratic equation.