85 . ( -51) + 34 . (-51) - 19 . (-51)
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29/19.49/51+29/19.34/51-29/19.32/51
=29/19.(49/51+34/51-32/51)
=29/19.1
=29/19
\(\dfrac{29}{19}.\dfrac{49}{51}+\dfrac{29}{19}.\dfrac{34}{51}-\dfrac{29}{19}.\dfrac{32}{51}\)
\(=\dfrac{29}{19}.\left(\dfrac{49}{51}+\dfrac{34}{51}-\dfrac{32}{51}\right)\)
\(=\dfrac{29}{19}.1\)
\(=\dfrac{29}{19}\)
34*86+51*86+85*14
=86*(34+51)+85*14
=86*85+85*14
=85*(86+14)
=85*100
=8500
\(34\cdot86+51\cdot86+85\cdot14\)
\(=(34+51)\cdot(86+14)\)
\(=85\cdot100=8500\)
Chúc bạn học tốt
Đặt A = 34/7x13 + 51/13x22 + 85/22x37 + 68/37x49
\(A=17x\left(\frac{2}{7x13}+\frac{3}{13x22}+\frac{5}{22x37}+\frac{4}{37x49}\right)\)
\(\frac{3}{17}xA=\frac{6}{7x13}+\frac{9}{13x22}+\frac{15}{22x37}+\frac{12}{37x49}\)
\(\frac{3}{17}xA=\frac{1}{7}-\frac{1}{13}+\frac{1}{13}-\frac{1}{22}+\frac{1}{22}-\frac{1}{37}+\frac{1}{37}-\frac{1}{49}\)
\(\frac{3}{17}xA=\frac{1}{7}-\frac{1}{49}\)
\(\frac{3}{17}xA=\frac{6}{49}\)
\(A=\frac{6}{49}:\frac{3}{17}\)
\(A=\frac{6}{49}x\frac{17}{3}=\frac{34}{49}\)
\(85\left(-51\right)+34\left(-51\right)-19\left(-51\right)\)
\(=\left(-51\right)\left(85+34-19\right)\)
\(=-51\cdot100=-5100\)
\(85\cdot\left(-51\right)+34\cdot\left(-51\right)-19\cdot\left(-51\right)\)
⇔\(\left[-51\right]\left(85+34-19\right)\)
= \(\left[-51\right]\cdot100\)
\(=-5100\)