Đáp án:
Giải thích các bước giải:
a) Rút gọn: 5.6 + 5.7 5.8 + 20 = 5.6 + 5.7 5.8 + 5.4 = 5. ( 6 + 7 ) 5. ( 8 + 4 ) = 5.13 5.12 = 13 12 5.6+5.75.8+20=5.6+5.75.8+5.4=5.(6+7)5.(8+4)=5.135.12=1312 8.9 − 4.15 12.7 − 180 = 2.4.3 2 − 4.3.5 12.7 − 12.15 = ( 2.3 ) . ( 4.3 ) − ( 4.3 ) .5 12. ( 7 − 15 ) = 6.12 − 12.5 12. ( − 8 ) = 12. ( 6 − 5 ) − 8.12 8.9−4.1512.7−180=2.4.32−4.3.512.7−12.15=(2.3).(4.3)−(4.3).512.(7−15)=6.12−12.512.(−8)=12.(6−5)−8.12 = 12.1 − 8.12 = − 1 8 12.1−8.12=−18 Quy đồng: MC(mẫu chung): 24 Ta có: 13 12 = 13.2 12.2 = 26 24 1312=13.212.2=2624, − 1 8 = − 3 8.3 = − 3 24