X partly constant and partly varies as y when x =7,y=3 when x =9 and y =6

Question

(a) find the relationship equation between x and y
(b) find x when y=4

Answer 1

x = c + ky
When x=7, y=3
7 = c + 3k
when x = 9, y = 6
9 = c + 6k
subtract them,
2 = 3k
k = 2/3
sub into the first equation: 7 = c + 3k
c = 7 - 3(2/3) = 7 - 2 = 5

x = 5 + (2/3)y

sub in y = 4 to find x

Answer 2

X=5+2/3×4+4=23/3

Answer 3

5.6666666667

Answer 4

Yes, the decimal approximation for 23/3 is 7.6666666667, which rounds to 5.6666666667 when rounded to ten decimal places.