Question

先化简下式，再取一个你喜欢的数代入求值：7a-2[3a²+(2+3a-a²)]

Answer 1

解：原式=7a-2[3a²+2+3a-a²]
              =7a-6a²-4-6a+2a²
              =(-6+2)a²+(7-6)a-4
              =-4a²+a-4
当a=1时，原式=-4×1+1-4
                       =-7