9×1.2^2-16×1.4^2 用因式分解计算
问题描述：
9×1.2^2-16×1.4^2 用因式分解计算
答
9×1.2^2-16×1.4^2
=(3×1.2)²-(4×1.4)²
=(3×1.2+4×1.4)(3×1.2-4×1.4)
=(3.6+5.6)(3.6-5.6)
=9.2×(-2)
=-18.4