Answer:
Part 1) The slope of JK is 
 
 
Part 2) The slope of KL is 
 
 
Part 3) The slope of JL is 
 
 
Part 4) Triangle JKL is a right triangle because two of these slopes have a product of -1
Explanation:
we know that
If two lines are perpendicular, then their slopes are opposite reciprocal (the product of their slopes is equal to -1)
The formula to calculate the slope between two points is equal to 
 
 
we have

Part 1) Find the slope JK
we have

substitute in the formula
 
 
 
 
Part 2) Find the slope KL
we have

substitute in the formula
 
 
 
 
 
 
Part 3) Find the slope JL
we have

substitute in the formula
 
 
 
 
 
 
Part 4) Compare the slopes
 
 
 
 
 
 
we have that
JK and KL are perpendicular because their slopes are opposite reciprocal
The product of their slopes is equal to -1
therefore
Triangle JKL is a right triangle because two of these slopes have a product of -1