1)(- 5) × (+ 6) + (-4) × (- 8) = (- 30) + (+32)= 32 - 30 = 2
2)0,25+1/2 =[tex]0,25+ \frac{1}{2}= \frac{25}{100}+ \frac{1}{2}= \frac{1}{4} + \frac{1}{2}= \frac{1+2}{4}= \frac{3}{4} [/tex]
3) {a,b,c} dp. {2,3,4}
a/2 = b/3 = b/4 = k
a = 2k, b = 3k, c = 4k
2k + 3k + 4k = ??????????