1/x + 1/y = 2 4/x + 2/y = 7 Maka 3x + 5y =

jawab

1/x = a
1/y= b

a+ b = 2.......}kali 2
4a + 2b = 7

2a + 2b = 4
4a + 2b = 7 ...|(-)
-2a = - 3
a = 3/2
 
a + b = 2
b = 2 - a
b = 2 - 3/2
b = 1/2

a = 3/2 → x = 2/3
b = 1/2 → y= 2

nilai 3x + 5y = 3(2/3) + 5(2)
= 2 +10
= 12