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Mathematics

Find the equation of the line that is perpendicular to 3x + 2y - 8 = 0 and passes through the mid-point of the line segment joining the points (5, -2) and (2, 2).

Straight Line Eq

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Answer

Given equation of line,

⇒ 3x + 2y - 8 = 0

Converting it in the form y = mx + c,

⇒ 2y = -3x + 8

⇒ y = 32x+4-\dfrac{3}{2}x + 4

Comparing with y = mx + c we get,

Slope (m1) = 32-\dfrac{3}{2}

Now, the coordinates of the mid-point of the line segment joining the points (5, -2) and (2, 2) will be

(5+22,2+22)(72,0).\Rightarrow \Big(\dfrac{5 + 2}{2}, \dfrac{-2 + 2}{2}\Big) \\[1em] \Rightarrow \Big(\dfrac{7}{2}, 0\Big).

Let's consider the slope of the line perpendicular to the given line be m2.

Then,

m1×m2=132×m2=1m2=23.\Rightarrow m1 \times m2 = -1 \\[1em] \Rightarrow -\dfrac{3}{2} \times m2 = -1 \\[1em] \Rightarrow m2 = \dfrac{2}{3}.

The equation of the new line with slope m2 and passing through (72,0)(\dfrac{7}{2}, 0) can be given by point-slope form i.e.,

y - y1 = m(x - x1)

Putting values we get,

y0=23(x72)3y=2(x72)3y=2x72x3y7=0.\Rightarrow y - 0 = \dfrac{2}{3}(x - \dfrac{7}{2}) \\[1em] \Rightarrow 3y = 2(x - \dfrac{7}{2}) \\[1em] \Rightarrow 3y = 2x - 7 \\[1em] \Rightarrow 2x - 3y - 7 = 0.

Hence, the equation of the line is 2x - 3y - 7 = 0.

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