18 + 2 = ?
Tìm A=(2-1/18)×(2-2/18)×(2-3/18)×(2-4/18)×....×(2-100/18)
Giúp mình với ạ.
\(A=\left(\frac{2.18-1}{18}\right)\left(\frac{2.18-2}{18}\right)\left(\frac{2.18-3}{18}\right)....\left(\frac{2.18-35}{18}\right)\left(\frac{2.18-36}{18}\right)\left(\frac{2.18-37}{18}\right)...\left(\frac{2.18-100}{18}\right)\)
\(=\frac{35}{18}.\frac{34}{18}.\frac{33}{18}...\frac{1}{18}.\frac{0}{18}.\frac{-1}{18}...\frac{-64}{18}=0\)
Đúng ghi Đ, sai ghi S:
a) 32 : 4 : 2 = 8 : 2 = 4
32 : 4 : 2 = 32 : 2 = 16
b) 18 : 2 x 3 = 18 : 6 = 3
18 : 2 x 3 = 9 x 3 = 18
a) 32 : 4 : 2 = 8 : 2 = 4
32 : 4 : 2 = 32 : 2 = 16
b) 18 : 2 x 3 = 18 : 6 = 3
18 : 2 x 3 = 9 x 3 = 18
18 mũ 18 : 18 mũ 17 + 2 mũ 3 . 3 mũ 2
\(18^{18}:18^{17}+2^3.3^2=18^{18-17}+8.9=18+72=90\)
Trong chương trình bảng tính, công thức nào sau đây là đúng:
A. = (18+ 6)*3 / 2^3
B. = (18+ 6).3 / 2 3
C. = (18+6).3 / 2^3
D. = (18+6)*3 : 2 3
Giúp với nhé ^^
Tính A = \(\left[2-\frac{1}{18}\right].\left[2-\frac{2}{18}\right].\left[2-\frac{3}{18}\right]...\left[2-\frac{100}{18}\right]\)
[1/18+2/17+.......18/1+18] : [1/18+1/17+...+1/1]
Đặt A = \(\frac{\frac{1}{18}+\frac{2}{17}+....+\frac{18}{1}+18}{\frac{1}{18}+\frac{1}{17}+....+\frac{1}{1}}\)
Xét TS (tử số) của A ta có:
TS = \(\frac{1}{18}+\frac{2}{17}+...+\frac{18}{1}+18\)
\(TS=\left(\frac{1}{18}+1\right)+\left(\frac{2}{17}+1\right)+...+\left(\frac{18}{1}+1\right)\) (chia 18 ra 18 phần 1 đơn vị cộng lại cho mỗi phân số)
\(TS=\frac{19}{18}+\frac{19}{17}+...+\frac{19}{1}=19.\left(\frac{1}{18}+\frac{1}{17}+...+\frac{1}{1}\right)\)
Thay lại TS vào A ta có:
\(A=\frac{19.\left(\frac{1}{18}+\frac{1}{17}+...+\frac{1}{1}\right)}{\left(\frac{1}{18}+\frac{1}{17}+...+\frac{1}{1}\right)}=19\)
a) 135 + (-2) . 14 -135 + 28
b) -18 . 2 +18 . (-6) + (-18) . 3
Đáp án :
a) \(135+\left(-2\right).14-135+28\)
\(=135+\left(-28\right)-135+28\)
\(=135-28-135+28\)
\(=135-135+28-28=0\)
b) \(-18.2+18.\left(-6\right)+\left(-18\right).3\)
\(=18.\left(2+6+3\right)=18.11=198\)
a) \(135+\left(-2\right)\cdot14-135+28\)
\(=135+\left(-28\right)-135+28\)
\(=\left(135-135\right)+\left[\left(-28\right)+28\right]\)
\(=0+0\)
\(=0\)
b) \(-18\cdot2+18\cdot\left(-6\right)+\left(-18\right)\cdot3\)
\(=-18\cdot2+\left(-18\right).6+\left(-18\right).3\)
\(=-18\cdot\left(2+6+3\right)\)
\(=-18\cdot11\)
\(=-198\)
a) 135 + (-2) . 14 - 135 +28
b) -18 . 2 + 18 . (-6) + (-18) . 3
\(a)135+\left(-2\right).14-135+28\)
\(=135+\left(-28\right)-135+28\)
\(=135-135+\left(-28\right)+28\)
\(=0+0\)
\(=0\)
\(b)\left(-18\right).2+18.\left(-6\right)+\left(-18\right).3\)
\(=\left(-36\right)+\left(-108\right)+\left(-54\right)\)
\(=\left(-144\right)+\left(-54\right)\)
\(=\left(-198\right)\)
-18 . 2 + 18 .(-6) + (-18) . 3
\(-18.2+18.\left(-6\right)+\left(-18\right).3\)
\(=-18.2+\left(-18\right).6+\left(-18\right).3\)
\(=-18.\left(2+6+3\right)\)
\(=-18.11\)
\(=-198\)
-18.2+(-18).6+(-18).3
=-18.(2+6+3)
=-18.12
= ..... ( tự tính nha )
-18×2+18×(-6)+(-18)×3. =18×(-2)+18×(-6)+18×(-3) =18×[-2+(-6)+(-3)]. =18×(-11). =-189
\(x\sqrt{18}-\sqrt{18}=x\sqrt{18}+4\sqrt{2}\)
\(x\sqrt{18}-\sqrt{18}=x\sqrt{18}+4\sqrt{2}\\ \Rightarrow-3\sqrt{2}=4\sqrt{2}\left(vô.lí\right)\)
\(x\sqrt{18}-\sqrt{18}=x\sqrt{18}+4\sqrt{2}.\)
\(\Leftrightarrow x\sqrt{18}-\sqrt{18}-x\sqrt{18}=4\sqrt{2}.\)
\(\Leftrightarrow-3\sqrt{2}=4\sqrt{2}\) (vô lý).
<=> x\(\sqrt{18}\) - x\(\sqrt{18}\) = \(4\sqrt{2}\) + \(\sqrt{18}\)
<=> 0x = \(4\sqrt{2}\) + \(3\sqrt{2}\)
<=>0x = \(7\sqrt{2}\)