1. Rút gọn
A= -56.49+(-49).44/73.14+(-14).(-27)
B=2^6.39+4^3.24/(-4)^2.17+2^4.46
help me
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a) \(\dfrac{5}{6}-\dfrac{2}{14}\)
\(=\dfrac{5}{6}-\dfrac{1}{7}\)
\(=\dfrac{35}{42}-\dfrac{6}{42}\)
\(=\dfrac{29}{42}\)
b) \(\dfrac{5}{20}-\dfrac{1}{6}\)
\(=\dfrac{1}{4}-\dfrac{1}{6}\)
\(=\dfrac{3}{12}-\dfrac{2}{12}\)
\(=\dfrac{1}{12}\)
c) \(\dfrac{5}{9}-\dfrac{3}{12}\)
\(=\dfrac{5}{9}-\dfrac{1}{4}\)
\(=\dfrac{20}{36}-\dfrac{9}{36}\)
\(=\dfrac{11}{36}\)
d) \(8-\dfrac{4}{6}\)
\(=\dfrac{48}{6}-\dfrac{4}{6}\)
\(=\dfrac{44}{6}=\dfrac{22}{3}\).
\(4x^2-28x+49=\left(2x\right)^2-2\cdot2x\cdot7+7^2=\left(2x-7\right)^2\)
Khi x=4 thì \(4x^2-28x+49=\left(2x-7\right)^2=\left(2\cdot4-7\right)^2=1\)
\(A=2\sqrt{27}-\sqrt{\left(1-\sqrt{3}\right)^2}+\dfrac{1}{2-\sqrt{3}}\\ =2.3\sqrt{3}-\left|1-\sqrt{3}\right|+\dfrac{2+\sqrt{3}}{\left(2-\sqrt{3}\right)\left(2+\sqrt{3}\right)}\\ =6\sqrt{3}-\left(-1+\sqrt{3}\right)+\dfrac{2+\sqrt{3}}{2^2-\sqrt{3^2}}\\ =6\sqrt{3}+1-\sqrt{3}+2+\sqrt{3}\\ =6\sqrt{3}+3\)
\(a,=\left(2x-7\right)^2=\left(2.4-7\right)^2=1\)
\(b,\left(x-3\right)^3=\left(5-3\right)^3=8\)
Bài 1: Rút gọn
\(A=\dfrac{-56\cdot49+\left(-49\right)\cdot44}{73\cdot14+\left(-14\right)\cdot\left(-27\right)}\)
\(=\dfrac{49\cdot\left(-56-44\right)}{14\cdot\left(73+27\right)}\)
\(=\dfrac{-49\cdot100}{14\cdot100}=\dfrac{-7}{2}\)