Diketahui x²=4y+49 dan y²=4x+49 maka nilai dari 1/2 xy adalah...?
![]()
Jawab:
x²=4y+49 dan y²=4x+49
4y = x² - 49
4x= y² - 49__( - )
4y - 4x = x² -y²
-4(x - y) = (x +y)(x - y)
x + y= - 4
(x + y)² = x² + y² + 2xy
(-4)² = 4y + 49 + 4x + 49 + 2xy
16 = 4x+ 4y + 98 + 2xy
16 = 4(x + y) + 98+ 2xy
16 = 4(-4) + 98 + 2xy
16 = - 16 + 98 + 2xy
16= 82 + 2xy
2xy = 16 - 82
2xy = - 66
xy = - 33
1/2 (xy ) = -33/2
[answer.2.content]