Answer:
Rule of 9 : an integer is divisible by 9 if and only if the sum of its integers is divisible by 9.
Proof :
Let us consider a number x such that,
Where, 
are the the digits of the number x,
So, we can write,
Let,
Since, a number is in the form of 
, where k is an positive integer, is always divisible by 9,
⇒ 
are divisible by 9.
⇒ x-S is divisible by 9,
⇒ If S is divisible by 9 ⇒ x must divisible by 9,
Or if x is divisible by 9 ⇒ S must divisible by 9.
Hence, proved...
Which problem I don’t see any problem hear
Hey ok, let me work this problem out, could u give me the formal?
i cant find the notes so i need the formal.
Answer:
not possible to answer on text, very sorry we cant help
The slope of the given line is -4/5. The line perpendicular to that line will have a slope that is the opposite reciprocal. In other words, the perpendicular slope will be 5/4. If it passes through (4, 12), we have an x and a y value to use in y=mx+b. y is 12, x is 4, and we have a slope of 5/4. Filling in accordingly:
and 12 = 5 + b. So b = 7. Rewriting with our new slope and b value,
. And there you go!
