Mathematics 2007 JAMB Past Questions - Question 44: If the lines 2y-kx+2=0 and y+x-k/2=0 intersect at (1,-2),find the value of k.

Correct Answer

C

Explanation

2y -kx +2 =0, @ x = 1 , y = -22(-2) -k (1) +2 = 0, -4 - k +2 = 0, k = -2Or y+x -k/2 = 0 @ x = 1, y = -2-2 +1 -k/2 = 0 , -1 = k/2 To find the value of k, we can substitute the coordinates of the point of intersection (1, -2) into the equations of the lines and solve for k.For the first equation, 2y - kx + 2 = 0, substituting x = 1 and y = -2:2(-2) - k(1) + 2 = 0-4 - k + 2 = 0-2 - k = 0k = -2For the second equation, y + x - k/2 = 0, substituting x = 1 and y = -2:-2 + 1 - k/2 = 0-1 - k/2 = 0-k/2 = 1k = -2Therefore, the value of k is -2.therefore k = -1x2=-2