224k views
3 votes
I really really really need help!!!!

I really really really need help!!!!-example-1

1 Answer

6 votes
For
f to be continuous at
x=1, you need to have the limit from either side as
x\to1 to be the same.


\displaystyle\lim_(x\to1^-)f(x)=\lim_(x\to1^-)(|x-1|+2)=2

\displaystyle\lim_(x\to1^+)f(x)=\lim_(x\to1^+)(ax^2+bx)=a+b

If
a=2 and
b=3, then the limit from the right would be
2+3=5\\eq2, so the answer to part (1) is no, the function would not be continuous under those conditions.

This basically answers part (2). For the function to be continuous, you need to satisfy the relation
a+b=2.

Part (c) is done similarly to part (1). This time, you need to limits from either side as
x\to2 to match. You have


\displaystyle\lim_(x\to2^-)f(x)=\lim_(x\to2^-)(ax^2+bx)=4a+2b

\displaystyle\lim_(x\to2^+)f(x)=\lim_(x\to2^+)(5x-10)=0

So,
a and
b have to satisfy the relation
4a+2b=0, or
2a+b=0.

Part (4) is done by solving the system of equations above for
a and
b. I'll leave that to you, as well as part (5) since that's just drawing your findings.
User DextrousDave
by
8.1k points