21/47+9/45+26/47+36/45-1,5=
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\(\dfrac{21}{47}+\dfrac{9}{45}+\dfrac{26}{47}+\dfrac{4}{5}\)
\(=\left(\dfrac{21}{47}+\dfrac{26}{47}\right)+\left(\dfrac{9}{45}+\dfrac{4}{5}\right)\)
\(=1+1\)
\(=2\)
a,21.35-3.26.7
=735-546
=189
b,77-11.(30+7)
=77-407
=-330
c,85.(36-27)-35.(86-27)
=85.9-35.59
=765-2065
=1300
d,47.(43-15)-47.(45+15)
=47.28-47.60
=47.(28-60)
=47.(-32)=-1504
a)\(\dfrac{2}{5}-\dfrac{3}{7}+\dfrac{9}{45}\\ =\dfrac{2}{5}-\dfrac{3}{7}+\dfrac{1}{5}\\ =\dfrac{14-15+1}{35}\\ =\dfrac{0}{35}=0\)
b)\(\dfrac{5}{15}+\dfrac{14}{25}-\dfrac{12}{9}+\dfrac{2}{7}+\dfrac{11}{25}\\ =\left(\dfrac{1}{3}-\dfrac{4}{3}\right)+\left(\dfrac{14}{25}+\dfrac{11}{25}\right)+\dfrac{2}{7}\\ =-1+1+\dfrac{2}{7}\\ =0+\dfrac{2}{7}=\dfrac{2}{7}\)
\(a,\left(-37-17\right).\left(-9\right)+35.\left(-9-11\right)\)
\(=\left(-54\right).\left(-9\right)+35.\left(-20\right)\)
\(=486+\left(-700\right)\)
\(=-214\)
\(b,\left(-25\right).\left(75-25\right)-75.\left(45-25\right)\)
\(=\left(-25\right).50-75.20\)
\(=\left(-25\right).50+\left(-25\right).3.20\)
\(=\left(-25\right).50+\left(-25\right).60\)
\(=\left(-25\right).\left(50+60\right)\)
\(=\left(-25\right).110\)
\(=-2750\)
\(c,136.\left(-47\right)+36.47\)
\(=47.\left(-136+36\right)\)
\(=47.\left(-100\right)\)
\(=-4700\)
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50=1275
\(\frac{21}{47}+\frac{9}{45}+\frac{26}{47}+\frac{36}{45}-1,5\)
\(=\left(\frac{21}{47}+\frac{26}{47}\right)+\left(\frac{9}{45}+\frac{36}{45}\right)-1,5\)
\(=\frac{47}{47}+\frac{45}{45}\)
\(=1+1\)
=2