The equation of the plane which passes through the line of intersection of given plane is
→r=(^i+2^j+3^k)5+l[→r(2^i−4^j+^k)−3]=0.....(1)
It passes through the point (1,2,3) or (1^i+2^j+3^k)
(^i+2^j+3^k)(^i+2^j+3^k)+5+l(^i+2^j+3^k)(2^i−4^j+^k)=0
1+4+9+5+l[(2−68−3+3)]=0
19+l(−12)=0
l=1912
Putting value of l in equation (1)
→r(^i+2^j+3^k)+5+1912→r(2^i−4^j+^k)−3=0
→r(12^i+24^j+3^k+38^i−76^j+19^k)+2
→r(50^i+52^j+22^k)+2=0