If y varies directly s the square root of (x + 1) and y = 6 when x = 3, find x when y = 9
-
A.
8 -
B.
7 -
C.
6 -
D.
5
Correct Answer: Option A
Explanation
y (alpha) sqrt{x + 1}), y = ksqrt{x + 1})
6 = k(sqrt{3 + 1})
6 = k(sqrt{4})
6 = 2k
k = (frac{6}{2}) = 3
y = (sqrt{(x + 1)})
9 = 3(sqrt{(x + 1)})(divide both side by 3)
(frac{9}{3}) = (frac{3sqrt{x + 1}}{3})
3 = (sqrt{x + 1})(square both sides)
9 = x + 1
x = 9 – 1
x = 8