Đáp án:
`a. =2/5 xx 5-1/2 xx2=2/5 xx5-1/2 xx2=2-1=1`
`b. =1/2 xxsqrt{\frac{9}{100}}+5sqrt{\frac{81}{100}}=1/2 xx 3/10+5xx 9/10=3/20+9/2=93/20`
`c. = 2/5 xx 5/4-5/2 xx 2/5=2/5 xx 5/4-5/2 xx2/5=1/2-1=-1/2`
`d. =2/5 xx5-9/2 xx 4/9+12=2/5 xx5-9/2 xx 4/9+12=2-2+12=12`