Question

Decide which of the following are quadratic equations?

i. 9y² + 5 = 0 

ii. m³ – 5m² + 4 = 0 

iii. (l + 2)(l – 5) = 0

Answer 1

i. In the equation 9y² + 5 = 0, [y] is the only variable and maximum index of the variable is [2]. 

∴ It [is] a quadratic equation.

ii. In the equation m³ – 5m² + 4 = 0, [m] is the only variable and maximum index of the variable is not 2. 

∴ It [is not] a quadratic equation.

iii. (l + 2)(l – 5) = 0 

∴ l(l – 5) + 2(l – 5) = 0 

∴ l² – 5l + 2l – 10 = 0 

∴ l² – 3l – 10 = 0.

In this equation [l] is the only variable and maximum index of the variable is [2] 

∴ it [is] a quadratic equation.