Class 11 • Maths • Chapter 9
STRAIGHT LINES
True & False Quiz
Slope. Intercept. Infinity.
✓True
✗False
25
Questions
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Ch.9
Chapter
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XI
Class
Why True & False for STRAIGHT LINES?
How this format sharpens your conceptual clarity
🔵 Straight lines encode direction, rate of change and boundaries in 2D space — the simplest geometric objects.
✅ T/F tests slope conditions for parallel/perpendicular lines, various forms of line equations, and distance formulas.
🎯 Classic trap: a vertical line has UNDEFINED slope (not zero); horizontal line has slope ZERO.
📋
Read each statement carefully. Click True or False — instant feedback with explanation appears. Submit anytime; unattempted questions are marked Skipped.
Q 1
The general equation of a straight line in the plane can be written as \(ax+by+c=0\), where \(a\) and \(b\) are not both zero.
Q 2
The slope of the line parallel to the \(x\)-axis is zero.
Q 3
The slope of the line perpendicular to the \(x\)-axis is zero.
Q 4
If the slope of a line is positive, the line rises from left to right.
Q 5
The equation \(y=3\) represents a line parallel to the \(y\)-axis.
Q 6
The slope–intercept form of a straight line is \(y=mx+c\).
Q 7
The equation \(x=5\) represents a vertical line.
Q 8
Two lines having equal slopes are always coincident.
Q 9
The point \((0,0)\) lies on the line \(y=mx\) for all real values of \(m\).
Q 10
The intercept form of a line is \(\frac{x}{a}+\frac{y}{b}=1\).
Q 11
The slope of the line joining the points \((x_1,y_1)\) and \((x_2,y_2)\) is \(\frac{y_2-y_1}{x_2-x_1}\), provided \(x_1\neq x_2\).
Q 12
The angle between a line of slope \(m\) and the positive \(x\)-axis is given by \(\tan^{-1}m\).
Q 13
If two lines are perpendicular, the product of their slopes is 1.
Q 14
The equation of a line passing through \((x_1,y_1)\) with slope \(m\) is \(y-y_1=m(x-x_1)\).
Q 15
The distance between the parallel lines \(ax+by+c_1=0\) and \(ax+by+c_2=0\) is \(\frac{|c_1-c_2|}{\sqrt{a^2+b^2}}\).
Q 16
All lines of the form \(y=mx+c\) pass through the origin.
Q 17
The condition for three points \((x_1,y_1)\), \((x_2,y_2)\), and \((x_3,y_3)\) to be collinear is \(\begin{vmatrix}x_1&y_1&1\\x_2&y_2&1\\x_3&y_3&1\end{vmatrix}=0\).
Q 18
If the slopes of two lines are \(m_1\) and \(m_2\), then the tangent of the angle between them is \(\left|\frac{m_2-m_1}{1+m_1m_2}\right|\).
Q 19
The line \(ax+by+c=0\) cuts equal intercepts on the axes if and only if \(a=b\).
Q 20
The family of lines \(y=mx+1\) for different values of \(m\) all pass through a fixed point.
Q 21
The angle between the lines \(y=mx\) and \(y=-\frac{1}{m}x\) is \(90^\circ\) for all non-zero \(m\).
Q 22
The equation of the line perpendicular to \(ax+by+c=0\) has slope \(\frac{b}{a}\).
Q 23
If a line has infinite slope, it is parallel to the \(y\)-axis.
Q 24
The locus of a point moving such that its distances from the \(x\)-axis and \(y\)-axis are equal is the line \(y=x\).
Q 25
The angle between the lines \(ax+by=0\) and \(bx-ay=0\) is always \(90^\circ\).
Key Takeaways — STRAIGHT LINES
Core facts for CBSE Boards & JEE
1
Slope of x-axis = 0; slope of y-axis = undefined (tan90° undefined).
2
Parallel: m₁=m₂; Perpendicular: m₁×m₂=−1.
3
Slope-intercept: y=mx+c; Point-slope: y−y₁=m(x−x₁).
4
Intercept form: x/a+y/b=1; Normal form: x cosα+y sinα=p.
5
Distance between parallel lines ax+by+c₁=0 and ax+by+c₂=0 is |c₁−c₂|/√(a²+b²).
6
Three points are collinear iff the area of triangle they form equals zero.