TheUltimateWinner
A line \(l\) in the \(xy\)-coordinate system passes through the origin and point (\(m,n\)). Is \(m<n\)?
1) The line \(l\) has a negative slope
2) \(m<0\)
line equation : \(y= Mx+c\)
slope of a line passing through two points : \(M = (y2-y1)/(x2-x1)\)well, don't have to memorize it, since line passes through two points, the basic equation must satisfy these two points.
lets say two points be \(A: (x1, y1)\) and \(B: (x2, y2)\)
let line C passes through A and B
line C standard equation: \(y= Mx+c\)
now, since line C passes through \(A\) \((x1, y1)\) we have
\(y1 = Mx1+c \)
\(y1-Mx1 = c\)
since line C passes through \(B (x2, y2)\), we have
\(y2 = Mx2+c\)
from above we substitute c
\(y2= Mx2+y1-Mx1\)
or
\(y2-y1 = M(x2-x1)\)
\(M= (y2-y1)/(x2-x1)\\
\)
similarly, we can workout in this question toopoint 1: origin (0,0)
\(0 = 0+c => c=0\)
point 2: (m,n)
\(n=Mm+c\)
or \(M= (n-c)/m\)
from point 1 we get c=0
\(M= n/m\)QUESTION: \(m < n?\)STATEMENT 1 : slope M is negative\(M = n/m\)\(M < 0\)
either n can be \(< 0\)
or m can be \(< 0\)
therefore,
NOT SUFFICIENTSTATEMENT 2 : \(m<0\)no information about nwhat if n < m < 0therefore,
NOT SUFFICIENTcombining STATEMENT 1 and STATEMENT 2, we get
\(M < 0\) or \(n/m <0\)
and \(m < 0\)
which implies
\(n > 0 >m\)
and hence, \(n > m\)
therefore,
SUFFICIENT and Cplease give kudos, if you find this explanation helpful!!