Solve the inequality y2 - 3y > 18
A
-3 < y < 6
B
y 6
C
y > -3 or y > 6
D
y < 3 or y < 6
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
y\(^2\) - 3y > 18 = y\(^2\) - 3y - 18 > 0
y\(^2\) - 6y + 3y - 18 > 0 = y(y - 6) + 3 (y - 6) > 0
= (y + 3) (y - 6) > 0
Case 1 (+, +) \(\to\) (y + 3) > 0, (y - 6) > 0
= y > -3, y > 6
By simply substituting the value of y into the inequality, y > -3 is invalid, and y < 6 is also invalid.
Therefore, y < - 3 or y > 6
Source: Myschool Past Questions Archive (Record #31186)