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2023

Mathematics

JAMB

Find the equation of straight line passing through (2, 3) and perpendicular to the line 3x+2y+4=0

A.

3y = 5x - 2

B.

y = 5/3× − 2

C.

None of these

D.

3y = 2x + 5

Correct Answer: 3y = 2x + 5

Explanation

3x + 2y + 4 = 0 Rearrange: 2y = −3x − 4 Divide both sides by 2 y = (−3× − 4)/2 y = −3/2×−2 ∴ the gradient of the line 3x + 2y + 4 = 0 is −3/2 If two lines are perpendicular to each other ∴ m1xm2 = -1 Let m1 =−3/2 ∴ m2 = −1/m1 = −1/(−3/2) = 2/3 From the equation of a line which is given as m = (y − y1)/x − x1) where (x1, y1) = (2, 3) ∴ 2/3 = (y − 3)/x − 2) =3(y - 3) = 2(x - 2) = 3y - 9 = 2 x -4 = 3y = 2 x -4 + 9 ∴ 3y = 2x + 5

3x + 2y + 4 = 0 Rearrange: 2y = −3x − 4 Divide both sides by 2 y = (−3× − 4)/2 y = −3/2×−2 ∴ the gradient of the line 3x + 2y + 4 = 0 is −3/2 If two lines are perpendicular to each other ∴ m1xm2 = -1 Let m1 =−3/2 ∴ m2 = −1/m1 = −1/(−3/2) = 2/3 From the equation of a line which is given as m = (y − y1)/x − x1) where (x1, y1) = (2, 3) ∴ 2/3 = (y − 3)/x − 2) =3(y - 3) = 2(x - 2) = 3y - 9 = 2 x -4 = 3y = 2 x -4 + 9 ∴ 3y = 2x + 5
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