16 x ( 38 - 2 ) - 38 x ( 16-1 )
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Bài 1
a, -25 . 63 - 25 . 3
= 25 . (-63) - 25 . 3
= 25 . [(-63) - 3]
= 25 . (-66) = -1650
Bài 2
c, (x + 1)2 = 16
=> (x + 1)2 = 42
=> x + 1 = 4
=> x = 3
d, (-38) - (x - 2) = -16
=> (x - 2) = -38 - (-16)
=> x - 2 = -38 + 16 = -22
=> x = 2 + (-22)
=> x = -20

(dấu chấm là dấu nhân nha e)
*\(\dfrac{1}{2}\). \(\dfrac{1}{4}\)+\(\dfrac{3}{4}\)
= \(\dfrac{1}{8}\)+\(\dfrac{3}{4}\)
= \(\dfrac{1}{8}\)+\(\dfrac{6}{8}\)= \(\dfrac{7}{8}\)
*\(\dfrac{3}{4}\).\(\dfrac{5}{6}\).\(\dfrac{8}{15}\)
= \(\left(\dfrac{3}{4}.\dfrac{8}{15}\right)\).\(\dfrac{5}{6}\)
= \(\dfrac{2}{5}\).\(\dfrac{5}{6}\)
= \(\dfrac{1}{3}\)
*\(\dfrac{12}{19}\): \(\dfrac{17}{38}\).\(\dfrac{16}{9}\)
= \(\dfrac{12}{19}\). \(\dfrac{38}{17}\).\(\dfrac{16}{9}\)= 2,5


Bài 1:
a) −x + 8 = −17
−x = −17 − 8
−x = −25
⇒ x = 25
Vậy x = 25
b) 35 − x = 37
x = 35 − 37
x = −2
Vậy x = −2
c) x − 45 = −17
x = −17 + 45
x = 28
Vậy x = 28
d) |x + 1| = 20 (>0)
TH1: x + 1 = 20 TH2: x + 1 = −20
x = 20 − 1 x = −20 − 1
x = 19 x = −21
Vậy x∈\(\left\{-21;19\right\}\)
e) |x − 3| − 16 = −4
|x − 3| = −4 + 16
|x − 3| = 12 (>0)
TH1: x − 3 = 12 TH2: x − 3 = −12
x = 12+3 x = −12 + 3
x = 15 x = −9
Vậy x∈\(\left\{-9;15\right\}\)

ĐKXĐ: x<>0 và y<>0
\(\left\{{}\begin{matrix}\dfrac{38}{x}+\dfrac{64}{y}=3\\\dfrac{19}{x}+\dfrac{16}{y}=1\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}\dfrac{38}{x}+\dfrac{64}{y}=3\\\dfrac{38}{x}+\dfrac{32}{y}=2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{32}{y}=1\\\dfrac{19}{x}+\dfrac{16}{y}=1\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}y=32\\\dfrac{19}{x}=1-\dfrac{16}{32}=\dfrac{1}{2}\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}y=32\\x=38\end{matrix}\right.\left(nhận\right)\)

\(16.\left(38-2\right)-38.\left(16-1\right)\\ =16.36-38.15\\ =576-570\\ =6\)
16 x (38 -2) -38 x (16-1)
=16 x 36 - 38 x 15
=576 - 570
=6
đáp số:6