Answer:
x = - 4 or x = 20
Step-by-step explanation:
Given R is the midpoint of AM, then
RA = MR , substitute values
x² - 16x = 80 ( subtract 80 from both sides )
x² - 16x - 80 = 0 ← in standard form
(x - 20)(x + 4) = 0 ← in factored form
Equate each factor to zero and solve for x
x - 20 = 0 ⇒ x = 20
x + 4 = 0 ⇒ x = - 4
