题目

下面各题怎样简便就怎样算。① ÷[（25%+ ）×8]②91÷8÷1.25+32.6③4.5×436+0.55×43.6④1210÷[35×（ + ）]⑤101×110-73-37⑥ ÷[ ÷（ - ）] 答案：解：①79÷[（25%+13）×8] =79÷[712×8] =79÷143 =16 ②91÷8÷1.25+32.6 =91÷（8×1.25）+32.6 =91÷100+32.6 =0.91+32.6 =33.51 ③4.5×4.36+0.55×43.6 =（4.5+5.5）×4.36 =100×4.36 =436 ④1210÷[35×（ 15 + 37 ）] =1210÷[35×15+35×37] =1210÷[7+15] =1210÷22 =55 ⑤101×110-73-37 =101×110-110 =（101-1）×110 =100×110 =11000 ⑥813÷[19÷（34-23）] =813÷[19÷112] =813÷43 =613解方程：（1）x2-9=0   （2）x2-7x-18=O     （3）5x2=4x    （4）2x2+1=3x    （5）（x-3）2+4x（x-3）=0．