Question

if x-y=5 and xy=84, find the value of x+y​

Answer 1

Answer:

x+y   = 19

Step-by-step explanation:

given, x-y=5 and xy=84

consider (x-y)² =  x² - 2xy + y²

                   5² = x²+y² - 2(84)

                 25  = x²+y² - 168

              x²+y² = 25+168

              x²+y² = 193

so, (x+y)² = x² + 2xy + y²

               = x²+y² + 2(xy)

               = 193 + 2(84)

               = 193 + 168

               = 361

=> √(x+y)² = √361

=>     x+y   = 19