Answer:
5xy = - 13645
Step-by-step explanation:
Note that
(x - y)² = x² + y² - 2xy
Given
2x² + 2y² = 36 ( divide through by 2 )
x² + y² = 18
Then
(x- y)² = 74² = 5746 ← expand left side
x² + y² - 2xy = 5746 ← substitute x² + y² = 18
18 - 2xy = 5746 ( subtract 18 from both sides )
- 2xy = 5458 ( divide both sides by - 2 )
xy = - 2729
Thus
5xy = 5 × - 2729 = - 13645
