Question

Determine whether the values given against the quadratic equation are the roots of the equation.

x² + 4x – 5 = 0 , x = 1, –1

Answer 1

x² + 4x – 5 = 0, x = 1, –1 

For x = 1

\[ \left( 1 \right)^2 + 4\left( 1 \right) - 5 = 0\]

\[ \Rightarrow 1 + 4 - 5 = 0\]

\[ \Rightarrow 5 - 5 = 0\] 

So, x = 1 is a solution of the given equation. 

For x = –1 

\[\left( - 1 \right)^2 + 4\left( - 1 \right) - 5 = 0\]

\[ \Rightarrow 1 - 4 - 5 = 0\]

\[ \Rightarrow - 3 - 5 = 0\]

\[ \Rightarrow - 8 \neq 0\]

So, x = –1 is not a solution of the given equation.

Thus, only x = 1 is root of the given equation.