载:zǎi____ zài____ 挣:zhēng____ zhèng____ 兴:xīng____ xìng____
(4x+5x2−1−3x−1)÷x+2x2−2x+1 ,其中x=3.
(7.89+4.62)×15=( ____ )×15+4.62×( ____ )