Question

Bantuin dong please :)

dik. 2/x +3/y = 4
1/x-1/y = 1/2
tentukan. 1/(x+y)

Answer 1

2/x + 3/y = 4    | kali 1|
1/x - 1/y = 1/2  | kali 2|
__________________ -
3/y - (- 1/y) = 4 - (1/2)(2)
4/y = 4 - 1
4/y = 3
y = 4/3
susbtitusi:
2/x + 3/(4/3) = 4
2/x + 9/4 = 4
2/x = 7/4
x = 7/8

maka: 1/(x + y)
= 1/(4/3 + 7/8)
= 1/(32/24 + 21/24)
= 1/(53/24)
= 24/53

Answer 2

(2/x +3/y =4)×1 =2/x+3/y=4 ⇒2/x+3/y-4=0
(1/x-1/y=1/2)×2 =2/x-2/y=1 ⇒2/x-2/y-1=0

(2/x+3/y-4)-(2/x-2/y-1)
5/y-3⇒5/y=3
           y=5/3
2/x+3/y=4
2/x+3/(5/3)=4
2/x+9/5=4
2/x=4-9/5
2/x=11/5
            x=10/11

jadi 1/(x+y)=1/(10/11+5/3)
                 =1/(85/33
                 =33/85
                 =0,39