What is the equation of the line that passes through #(1,5)# and #(-2,14)# in slope intercept form?

2 Answers
Mar 25, 2018

#y=-3x+8#

Explanation:

#"the equation of a line in "color(blue)"slope-intercept form"# is

#•color(white)(x)y=mx+b#

#"where m is the slope and b the y-intercept"#

#"to calculate the slope m use the "color(blue)"gradient formula"#

#•color(white)(x)m=(y_2-y_1)/(x_2-x_1)#

#"let "(x_1,y_1)=(1,5)" and "(x_2,y_2)=(-2,14)#

#rArrm=(14-5)/(-2-1)=9/(-3)=-3#

#rArry=-3x+blarrcolor(blue)"is the partial equation"#

#"to find b substitute either of the 2 given points"#
#"into the partial equation"#

#"using "(1,5)" then"#

#5=-3+brArrb=5+3=8#

#rArry=-3x+8larrcolor(red)"in slope-intercept form"#

Mar 25, 2018

The reqd. equn. of the line is

#3x+y=8# or #y=-3x+8#

Explanation:

If #A(x_1,y_1) and B(x_2,y_2)#,then equation of the line:

#color(red)((x-x_1)/(x_2-x_1)=(y-y_1)/(y_2-y_1)#.

We have,

#A(1,5) and B(-2,14)#

So,

#(x-1)/(-2-1)=(y-5)/(14-5)#.

#=>(x-1)/-3=(y-5)/9#

#=>9x-9=-3y+15#

#=>9x+3y=15+9#

#=>9x+3y=24#

#=>3x+y=8# or #y=-3x+8#
graph{3x+y=8 [-20, 20, -10, 10]}