Find the zeros of the following function fx x2 18x 4Solut

Find the zero(s) of the following function. f(x) = x^2 - 18x - 4

Solution

f(x) = x² - 18x - 4

zeros of function ==> f(x) = 0

==> x² - 18x - 4 = 0

==> x² - 2(x)(9) - 4 = 0

add and substract 81 (i.e, 9²)

==> x² - 2(x)(9) + 9² - 9² - 4 = 0

==> (x - 9)² - 85 = 0            since a² - 2ab + b² = (a - b)²

==> (x - 9)² = 85

==> x - 9 = 85 , -85

==> x = 9 + 85 , 9 - 85

Hence zeros of function are 9 + 85 , 9 - 85