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Mathematics

(a) If the lines kx - y + 4 = 0 and 2y = 6x + 7 are perpendicular to each other, find the value of k.

(b) Find the equation of a line parallel to 2y = 6x + 7 and passing through (-1, 1)

Straight Line Eq

ICSE 2024

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Answer

(a) 1st equation :

⇒ kx - y + 4 = 0

⇒ y = kx + 4

Slope (s1) : k

2nd equation :

⇒ 2y = 6x + 7

⇒ y = 62x+72\dfrac{6}{2}x + \dfrac{7}{2}

⇒ y = 3x + 72\dfrac{7}{2}

Slope (s2) : 3

We know that,

Product of slope of perpendicular lines = -1

⇒ k × 3 = -1

⇒ k = 13-\dfrac{1}{3}

Hence, k = 13-\dfrac{1}{3}.

(b) We know that,

Slope of parallel lines are equal.

Slope of line parallel to line 2y = 6x + 7 is 3.

By point-slope form :

⇒ y - y1 = m(x - x1)

⇒ y - 1 = 3[x - (-1)]

⇒ y - 1 = 3[x + 1]

⇒ y - 1 = 3x + 3

⇒ y = 3x + 3 + 1

⇒ y = 3x + 4.

Hence, equation of line parallel to 2y = 6x + 7 and passing through (–1, 1) is y = 3x + 4.

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