Wir haben folgendes:
$$a\left [x+1+x(7b-1)\right ]+b\left [(1-2a)c+x(2c-3a)\right ]+2b\left [a(c-2x)-cx\right ] \\ =a\left [x+1+7bx-x\right ]+b\left [c-2ac+2cx-3ax\right ]+2b\left [ac-2ax-cx\right ] \\ =a\left [1+7bx\right ]+b\left [c-2ac+2cx-3ax\right ]+2b\left [ac-2ax-cx\right ] \\ =a+7abx+bc-2abc+2bcx-3abx+2abc-4abx-2bcx\\ = a+bc$$