Solution 2.2:5c

From Förberedande kurs i matematik 1

Two straight lines are parallel if they have the same slope. From the line y=3x+1, we can read off that it has a slope of 3 (the coefficient in front of x), and hence the equation we are looking for has an equation of the form

y=3x+m

where m is a constant. The condition that the line should also contain the point (-1,2) means that the point should satisfy the equation of the line

2=3(−1)+m

which gives m=5. Hence, the equation of the line is y=3x+5.