Question

How do you solve $ 2{x^2} + 3x - 4 = 0 $ using the quadratic formula?

Answer 1

Hint: A quadratic polynomial is defined as a polynomial of degree two and its zeros can be found using many methods like factorization, completing the square, graphs, quadratic formula etc. We use the quadratic formula when we fail to find the factors of the equation. In the given question, we are already told to solve the given quadratic equation using the quadratic formula, so for that, we will first express the given equation in the standard equation form and then the values of the coefficients are plugged in the quadratic formula.

Complete step-by-step answer:
The equation given is $ 2{x^2} + 3x - 4 = 0 $
On comparing the given equation with the standard quadratic equation
 $ a{x^2} + bx + c = 0 $ , we get –
 $ a = 2,\,b = 3,\,c = - 4 $
The Quadratic formula is given as –
 $ x = \dfrac{{ - b \pm \sqrt {{b^2} - 4ac} }}{{2a}} $
Now, put the known values in the above equation –
 $
  x = \dfrac{{ - 3 \pm \sqrt {{{(3)}^2} - 4(2)( - 4)} }}{{2(2)}} \\
   \Rightarrow x = \dfrac{{ - 3 \pm \sqrt {9 + 32} }}{4} \\
   \Rightarrow x = \dfrac{{ - 3 \pm \sqrt {41} }}{4} \;
  $
Hence the zeros of the given equation are $ \dfrac{{ - 3 + \sqrt {41} }}{4} $ and $ \dfrac{{ - 3 - \sqrt {41} }}{4} $ .
So, the correct answer is “ $ \dfrac{{ - 3 + \sqrt {41} }}{4} $ and $ \dfrac{{ - 3 - \sqrt {41} }}{4} $ ”.

Note: An algebraic expression that contains numerical values and alphabets too is known as a polynomial equation, but when the alphabets representing an unknown variable quantity are raised to some non-negative integer as the power, the algebraic expression becomes a polynomial equation. The degree of a polynomial equation is defined as the highest exponent of the unknown quantity in a polynomial equation. Now, various fields of mathematics require the point at which the value of a polynomial is zero, those values are called the factors/solution/zeros of the given polynomial. On the x-axis, the value of y is zero so the roots of an equation are the points on the x-axis that is the roots are simply the x-intercepts.