Find the value of discriminant of the following Equation.
$2{x^2} + x + 1 = 0$
$\left( A \right)7$
$\left( B \right) - 7$
$\left( C \right)9$
$\left( D \right) - 9$
Answer
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Hint: Here, given to find the discriminant of a quadratic equation. For example, let’s assume $a{x^2} + bx + c = 0$is an equation, and we have to find the discriminant of this equation. So, discriminant of equation denoted by $'\Delta '$and the formula for this is,
$ \Rightarrow \Delta = {b^2} - 4ac$ .
Complete step-by-step solution:
The given equation in the question is
$2{x^2} + x + 1 = 0$_ _ _ _ _ _ _ _ _ _$\left( 1 \right)$
To find the discriminant we have to compare the equation$\left( 1 \right)$ with,
$a{x^2} + bx + c = 0$_ _ _ _ _ _ _ _ _ _$\left( 2 \right)$
Compare $\left( 1 \right)$and $\left( 2 \right)$,
$ \Rightarrow a = 2,b = 1,c = 1$
Substitute the values in formula,
$\begin{align}
&\Rightarrow \Delta = {b^2} - 4ac \\
&\Rightarrow \Delta = {\left( 1 \right)^2} - 4 \times 2 \times 1 \\
&\Rightarrow \Delta = 1 - 8 \\
&\Rightarrow \Delta = - 7 \\
\end{align} $
Therefore, the value of the discriminant is $\Delta = - 7$ and the correct option is $\left( B \right)$.
Note: $ \Rightarrow $ If the discriminant value is positive, the quadratic equation has two real and distinct solutions.
$ \Rightarrow $ If the discriminant value is zero, the quadratic equation has only one solution or two real and equal solutions.
$ \Rightarrow $ If the discriminant value is negative, the quadratic equation has no real.
$ \Rightarrow \Delta = {b^2} - 4ac$ .
Complete step-by-step solution:
The given equation in the question is
$2{x^2} + x + 1 = 0$_ _ _ _ _ _ _ _ _ _$\left( 1 \right)$
To find the discriminant we have to compare the equation$\left( 1 \right)$ with,
$a{x^2} + bx + c = 0$_ _ _ _ _ _ _ _ _ _$\left( 2 \right)$
Compare $\left( 1 \right)$and $\left( 2 \right)$,
$ \Rightarrow a = 2,b = 1,c = 1$
Substitute the values in formula,
$\begin{align}
&\Rightarrow \Delta = {b^2} - 4ac \\
&\Rightarrow \Delta = {\left( 1 \right)^2} - 4 \times 2 \times 1 \\
&\Rightarrow \Delta = 1 - 8 \\
&\Rightarrow \Delta = - 7 \\
\end{align} $
Therefore, the value of the discriminant is $\Delta = - 7$ and the correct option is $\left( B \right)$.
Note: $ \Rightarrow $ If the discriminant value is positive, the quadratic equation has two real and distinct solutions.
$ \Rightarrow $ If the discriminant value is zero, the quadratic equation has only one solution or two real and equal solutions.
$ \Rightarrow $ If the discriminant value is negative, the quadratic equation has no real.
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