Tính nhanh:
b) (637.527-189):(526.637+448)
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Ta có:
\(\dfrac{637.527-189}{526.637+448}=\dfrac{637.\left(526+1\right)-189}{526.637+448}=\dfrac{637.526+637-189}{526.637+448}=\dfrac{637.526+448}{526.637+448}=1\)
**** cho minn nhe
637.527-189 =637.526+637.1-189 =637.526+448 =1
526.637+448 637.526+448 637.526+448
\(a)\)\(\left(1989.1990+3978\right)\div\left(1992.1991-3984\right)\)
\(=\)\(\left(1989.1990+1989.2\right)\div\left(1992.1991-1992.2\right)\)
\(=\)\(\left[1989.\left(1990+2\right)\right]\div\left[1992.\left(1991-2\right)\right]\)
\(=\)\(\left(1989.1991\right)\div\left(1992.1989\right)\)
\(=\)\(1\)
\(b)\)\(\left(637.527-189\right)\div\left(526.637+448\right)\)
\(=\)\(\left[637.\left(526-1\right)-189\right]\div\left(526.637-448\right)\)
\(=\)\(\left[637.526+\left(637-198\right)\right]\div\left(637.526-448\right)\)
\(=\)\(\left(636.526+448\right)\div\left(637.526-448\right)\)
\(=\)\(1\)
\(=\dfrac{637.\left(526+1\right)-189}{526.637+448}=\dfrac{637.526+637-189}{526.637+446}=\dfrac{637.526+448}{526.637+448}=1\)
\(\left(637.527-189\right):\left(526.637+448\right)\)
\(=\left(335699-189\right):\left(335062+448\right)\)
\(=335510:335510\)
\(=1\)
=335918.116
(thực hiện phép nhân, chia trước nha)
Học tốt
42x13-22x5+42x7-15x22
= 42 x (13+7) - 22 x (5+15)
= 42 x 20 - 22 x 20
= 20 x (42 - 22)
= 20 x 20 = 400
___
37x39+78x74+13x85+52x55
= 37 x 3 x 13 + 13 x 6 x 74 + 13 x 85 + 13 x 4 x 55
= 13 x (37 x 3+ 74 x 6+ 85 + 4 x 55)
= 13 x (111 + 444 + 85 + 220)
= 13 x 860 = 11180
(637x527-189):(526x637+448)
= (637 x 526 + 637 - 189): (526 x 637 + 448)
= (637 x 526 + 448) : (526 x 637 + 448) = 1
(637.527-189):(526.637+448)
= \(\frac{637.527-189}{526.637+448}\)
= \(\frac{637.\left(526+1\right)-189}{526.637+448}\)
= \(\frac{637.526+637-189}{526.637+448}\)
= \(\frac{637.526+448}{526.637+448}\)
= \(1\)