Given :
P1:2x−7y+4z−3=0P2:3x−5y+4z+11=0
Equation of the required plane can be written by using family of planes:
P1+λP2⇒(2x−7y+4z−3)+λ(3x−5y+4z+11)=0
It passes through (−2,1,3), so
(–4+7+12–3)+λ(–6–5+12+11)=0⇒−2+λ(12)=0⇒λ=16
Therefore, the equation of plane is
15x−47y+28z−7=0∴2a+b+c−7=30−47+28−7=4