X-12+21+34=?
Tính :
12 + 21 x 12 + 12 x 34
12 + 21 x 12 + 12 x 34
= 12 x ( 1 + 12 + 34 )
= 12 x 45
= 540
12 + 21 x 12 + 12 x 34
= 12 x 1 + 21 x 12 + 12 x 34
= 12 x (1+21+34)
= 12 x 56
= 672
Tính bằng cách thuận tiện nhất
a -(12/46 +15/21) +(3/7-7/23)
b(-21+-7/-9)-(6/34-25/9)
c (21/8--13/-26)+(34/16--12/52)
a) \(...=-\dfrac{12}{46}-\dfrac{15}{21}+\dfrac{3}{7}-\dfrac{7}{23}\)
\(=-\dfrac{12}{46}-\dfrac{7}{23}-\dfrac{15}{21}+\dfrac{3}{7}\)
\(=-\dfrac{6}{23}-\dfrac{7}{23}-\dfrac{5}{7}+\dfrac{3}{7}\)
\(=-\dfrac{13}{23}-\dfrac{2}{7}\)
\(=-\dfrac{13.7}{23.7}-\dfrac{2.23}{23.7}\)
\(=-\dfrac{91}{161}-\dfrac{46}{161}=-\dfrac{137}{161}\)
b) \(...=-21+\dfrac{7}{9}-\dfrac{3}{17}+\dfrac{25}{9}\)
\(=-21-\dfrac{3}{17}+\dfrac{7}{9}+\dfrac{25}{9}\)
\(=-21-\dfrac{3}{17}+\dfrac{32}{9}\)
\(=-\dfrac{3213}{153}-\dfrac{27}{153}+\dfrac{544}{153}=-\dfrac{2696}{153}\)
Tìm x:
A. 34 + (9 - 21)= 3417 - (x + 3417)
B. (15 - x) + (x - 12)= 7 - (-8 - x)
\(b,\left(15-x\right)+\left(x-12\right)=7-\left(-8-x\right)\)
\(\Leftrightarrow15-x+x-12=7+8+x\)
\(\Leftrightarrow3=15+x\)
\(\Leftrightarrow x=3-15\)
\(\Leftrightarrow x=-12\)
Vậy : \(x=-12\)
Mik sửa lại câu a cho bạn Đạt này
A. 34 + (9 - 21)= 3417 - (x + 3417)
<=>34 + (-12) = 3417 - x - 3417
<=>22 = -x
=> x = -22
Vậy x= -22
\(a,34+\left(9-21\right)=3417-\left(x+3417\right)\)
\(\Leftrightarrow34+13=3417-x-3417\)
\(\Leftrightarrow47=-x\)
\(\Leftrightarrow x=-47\)
Vậy : \(x=-47\)
42 x 2 =?
34 x2 =?
12 x 3 =?
21 x 3 =?
42 x 2 = 84
34 x2 = 68
12 x 3 = 36
21 x 3 = 63
42 x 2 = 84
34 x 2 = 68
12 x 3 = 36
21 x 3 = 63
k mk,mk k lại ^_-
42 x 2 = 84
34 x 2 = 68
12 x 3 = 36
21 x 3 = 63
12 + 32 + 34 x 0 + 65 + 21 =
kb với mk nha(nhất là ARMY)
-12/21:34/43
\(-\dfrac{12}{21}\div\dfrac{34}{43}\)
\(=-\dfrac{12}{21}\times\dfrac{43}{34}\)
\(=-\dfrac{86}{119}\)
\(-\dfrac{12}{21}:\dfrac{34}{43}=-\dfrac{12}{21}.\dfrac{43}{34}=-\dfrac{2}{7}.\dfrac{43}{17}=-\dfrac{86}{119}\)
21+34+36-12=
\(21+34+36-12\)
\(=\left(34+36\right)+\left(21-12\right)\)
\(=70+9\)
\(=79\)
Tìm X và Y biết :
a) 4/X = Y/14 = 12/21
b) 1/X - Y/4 = 2/34
1.Thực hiện phép tính hợp lý nếu có thể
a) x - (11 - 1) = -48 + (-12 + x)
b) 34 + (9 - 21) = 3471 = (x + 3471)
c) (15 - x ) + ( x - 12 ) = 7 - (-8 + x)