We need to find how many integers n satisfy \((n – 5) (n – 10) – 3(n – 2) ≤ 0\) ?\((n – 5) (n – 10) – 3(n – 2) ≤ 0\)
=> \(n^2\) -5n - 10n + 50 -3n + 6 ≤ 0
=> \(n^2\) -18n + 56 ≤ 0
=> \(n^2\) -14n -4n + 56 ≤ 0
=> n*(n - 14) - 4(n - 14) ≤ 0
=> (n - 14) * (n - 4) ≤ 0
Two ways to solve this now
Method 1: Logic(n - 14) * (n - 4) ≤ 0
Product of two numbers is ≤ 0
=> Either one is positive and other is negative or at least one is 0
0 case can come when n = 4 or 14
Lets solve for Either to be negative
If n < 4 then both (n - 4) and (n - 14) will be negative => NOT POSSIBLE
If n > 14 then both (n - 4) and (n - 14) will be positive => NOT POSSIBLE
If 4 ≤ n ≤ 14 then (n - 14) * (n - 4) ≤ 0
=> Possible values are from 4 to 14 inclusive
=> 14 - 4 + 1 = 11 values
Method 2: Sine Wave / Curvy MethodWe will plot 4 and 14 on the number line and put a filled dot on those two numbers to indicate that both are included. Refer below image:
Attachment:
4 to 14.jpg [ 13.27 KiB | Viewed 1905 times ]
Since the inequality sign is ≤ so we will take the values in "-" range
=> 4 ≤ n ≤ 14
=> 11 integer values are possible.
So,
Answer will be DHope it helps!
Watch the following video to learn How to Solve Inequality Problems