Straight Lines · JEE Preparation Mathematics

Find the equation of the line that passes through the point of intersection of 2x + 3y - 7 = 0 and x - y + 1 = 0, and is perpendicular to x + 2y - 5…

Practice question from Straight Lines (JEE Preparation Mathematics), with the correct answer and a step-by-step solution.

medium · Subjective · Q-4B1111

Find the equation of the line that passes through the point of intersection of 2x + 3y - 7 = 0 and x - y + 1 = 0, and is perpendicular to x + 2y - 5 = 0.

Answer: The two given lines intersect at (4/5, 9/5). The line x + 2y - 5 = 0 has slope -1/2, so the required perpendicular line has slope 2. Therefore, its equation is y - 9/5 = 2(x - 4/5), or 10x - 5y + 1 = 0.

Solution

Solving 2x+3y−7=02x+3y-7=0 and x−y+1=0x-y+1=0 gives (x,y)=(45,95)(x,y)=\left(\frac45,\frac95\right). The slope of x+2y−5=0x+2y-5=0 is −12-\frac12, so the required perpendicular slope is 22. Hence, y−95=2(x−45)y-\frac95=2\left(x-\frac45\right), or 10x−5y+1=010x-5y+1=0.

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