Tính nhanh : a,(7256.4375-725) : ( 4375.7255+3650) b, ( 456.11+912) : ( 13.74 ) Giúp mk với nhé

` a) ` ` \frac{7256.4375 – 725}{4375.7255 + 3650} `

` = \frac{(7255 + 1).4375 – 725}{4375.7255 + 3650} `

` = \frac{7255.4375 + 4375 – 725}{4375.7255 + 3650} `

` = \frac{7255.4375 + 3650}{4375.7255 + 3650} `

` = 1 `

` b) ` ` \frac{456.11 + 912}{13.74} `

` = \frac{(74 + 382).11 + 912}{(11 + 2).74} `

` = \frac{74.11 + 4202 + 912}{11.74 + 148} `

` = \frac{74.11 + 5114}{11.74 + 148} `

` = (74.11).\frac{1}{11.74} + (74.11).\frac{1}{148} + 5114.\frac{1}{11.74} + 5114.\frac{1}{148} `

` = 1 + 11/2 + \frac{2557}{407} + \frac{2557}{74} `

` = 228/37 `