Question

How do you find value of discriminant then describe number and type of solutions for `x^2 - 21 = 4x`?

Answer 1

First rearrange the equation into standard form, `x^2-4x-21=0`. The discriminant is then `(-4)^2-4*1*(-21)=16+84=100`. Given that the discriminant is positive, there are two real roots.

Explanation:

Standard form for a quadratic equation is `ax^2+bx+c=0`.

Once the equation has been arranged in this form, the discriminant is given by `b^2-4ac`.

If the discriminant is positive there are two real roots, if it is negative there are two imaginary roots, if it is zero there is one real root.