解:4x^2+4x+1+3(x^2-4x+4)-4=7(x^2-9)7x^2-8x+9=7x^2-63-8x=-72x=9
先展开得:4x^2+4x+1+3x-12x+12-4=7x^2-63-8x+9=-638x=72x=9