1.

A straight line is drawn through a given point `P(1,4)dot`Determine the least value of the sum of the intercepts on thecoordinate axes.

Answer» `y-y_1=m(x-x_1)`
`(x_1,y_1)=(1,4)`
`y-y_!=m(x-1)`
at y intercept,x=0
`y=4-m`
at x intercept,y=0
`x-1=-4/m`
`x=(m-4)/m`
`S=((m-4)/m)+(4-m)`
`(dS)/(dm)=(0+4/m^2-1)=0`
`4/m^2=1`
`m=pm2`
`(d^2S)/(dm^2)=-8/m^3`
When m=2,`(d^2S)/(dm^2)=-8/8=-1<0`
This will be maximum
When m=-2,`(d^2S)/(dm^2)=-8/-8=1>0`
This will be minimum
`x=(m-4)/m=(-2-4)/(-2)=3`
`y=4-m=4+2=6`
S=3+6=9.


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