1)(2a+c)(a-3c)+a(2c-a)=2a²-6ac+ac-3c²+2ac-a²=a²-3ac-3c².
2) 2(x+6)²-(20x+70)=2(x²+12x+36)-20x-70 = 2x²+24x+72-20x-70=2x²+4x+2.
1)(2a+c)(a-3c)+a(2c-a)=2a²-6ac+ac-3c²+2ac-a²=a²-3ac-3c².
2) 2(x+6)²-(20x+70)=2(x²+12x+36)-20x-70 = 2x²+24x+72-20x-70=2x²+4x+2.