4: \(\frac{28}{42}=\frac{28:14}{42:14}=\frac23\)
\(\frac{60}{135}=\frac{60:15}{135:15}=\frac49\)
\(\frac{288}{180}=\frac{280:36}{180:36}=\frac85\)
2:
a: ƯCLN(1;16)=1
b: \(8=2^3;20=2^2\cdot5\)
=>ƯCLN(8;20)=\(2^2=4\)
c: \(84=2^2\cdot3\cdot7;156=2^2\cdot3\cdot13\)
=>ƯCLN(84;156)=\(2^2\cdot3=12\)
d: \(16=2^4;40=2^3\cdot3;176=2^4\cdot11\)
=>ƯCLN(16;40;176)=\(2^3=8\)
