c) 53 – 7x = 57 : 55
a) -2x - (-17)= 9 b) 11 + (15 – x) = 1
c) 53 – 7x = 57 : 55 | d) 29 +9.x2 = 110 |
e) (2x-4).(3-x) = 0
g) 2x + 1 chia hết cho x -2 |
a: =>-2x=9-17=-8
hay x=4
b: =>15-x=-10
hay x=25
d: \(\Leftrightarrow9x^2=81\)
hay \(x\in\left\{3;-3\right\}\)
e: \(\Leftrightarrow\left[{}\begin{matrix}2x-4=0\\3-x=0\end{matrix}\right.\Leftrightarrow x\in\left\{2;3\right\}\)
a) -2x - (-17)= 9 b) 11 + (15 – x) = 1
c) 53 – 7x = 57 : 55 |
b) 11 + (15 – x) = 1
d) 29 +9.x2 = 110
e) (2x-4).(3-x) = 0
g) 2x + 1 chia hết cho x -2
b: =>15-x=-10
hay x=25
a: =>-2x+17=9
=>-2x=-8
hay x=4
d: \(\Leftrightarrow9x^2=81\)
hay \(x\in\left\{3;-3\right\}\)
e: \(\Leftrightarrow\left[{}\begin{matrix}2x-4=0\\3-x=0\end{matrix}\right.\Leftrightarrow x\in\left\{2;3\right\}\)
49-51+53-55+57-59+61
(49-51)+(53-55)+(57-59)+61
= -2-2-2+61=55
49-51+53-55+57-59
=(49-51)+(53-55)+(57-59)+61
=-2+(-2)+(-2)+61
=55
49-51+53-55+57-59+61+-63
ta có số hạng thứ 25 của A
là : \(7+24\times2=7+48=55\)
vậy chọn đáp án B
49-51+53-55+57-59+61-63+65
49-51+53-55+57-59+61-63+65=57
chúc bạn học tốt
^^
49-51+53-55+57-59+61-63+65
=(49+-51)+(53+-55)+(57+-59)+(61+-63)+65
=-2+-2+-2+-2+65
=-8+65
=57
Nhớ k cho mình nha mệt lắm đó
bỏ ngoặc rồi tính
(57-725)-(605-53)
(55+45+15)-(15-55+45)
57-725-605+53=-1220
55+45+15-15+55-45=110
Ủng hộ mk nhaaa
Câu 1:
= 57 - 725 - 605 - 53
= ( 725 - 605 ) - ( 57 - 53 )
= 120 - 4
= 116
Câu 2 làm tương tự
Tính bằng cách hợp lí:
49 - 51 + 53 - 55 + 57 - 59 + 61 - 63 + 65
\(49-51+53-55+57-59+61-63+65\\ =\left(49-51\right)+\left(53-55\right)+\left(57-59\right)+\left(61-63\right)+65\\ =-2+-2+-2+-2+65\\ =-8+65=57\)
49 - 51 + 53 - 55 + 57 - 59 + 61 - 63 + 65
= ( 49 - 51 ) + ( 53 - 55 ) + ( 57 - 59 ) + ( 61 - 63 ) + 65
= (-2) + (-2) + (-2) + (-2 ) + 65
= (-2) . 4 + 65
= (-8) + 65
= 57
Tính tổng sau :
B = 1 + 22 + 24 + 26 + 28 + ... + 2200
C = 5 + 53 + 55 + 57 + ... + 5101
\(B=1+22+24+26+28+...+2200\)
\(=1+\dfrac{\left(2200+22\right).\left[\left(2200-22\right):2+1\right]}{2}\)
\(=1+\dfrac{2222.1090}{2}\)
\(=1+1210990\)
\(=1210991\)
\(C=5+53+55+57+...+5101\)
\(=5+\dfrac{\left(5101+53\right).\left[\left(5101-53\right):2+1\right]}{2}\)
\(=5+\dfrac{5154.2525}{2}\)
\(=5+6506925\)
\(=6506930\)