Let equations of two planes
a1x + b1y + c1z + d1 = 0 ...(1)
and a2x + b2y + c2z + d2 = 0 ... (2)
In figure, plane PQ and RS intersect in line AB. Thus, AB is a intersecting line.
∵ Planes (1) and (2) intesect in a line, then we suppose that the point (x'1 y'1, z'1) lies on this line. Because this point is on the intersect line, thus its coordinate satisfy (1) and (2).
a1x' + b1y’ + c1z' + d1 = 0 ...(3)
and a2x' + b2y' + c2z' + d2 = 0 ...(4)
Multiplying equation (4) by any constant X and adding in equation (3), we get
(a1x' + b1y' + C1z' + d1) + λ(a2x' + b2y' + c2z' + d2) = 0
⇒ (a1 + λa2)x' + (b1 + λb2)y' + (c1 + λc2)z' + d1 + λd2 = 0
∴ Required plane
(a1 + λa2)x + (b1 + λb2)y + (c1 + λc2)z + (d1 + λd2) = 0 Value of λ can be find by the given condition.