18 x 3 = ?
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
X x 18 -18 =X x 3 -17
X x 18 -18 =X x 3 -17
X x 18 - X x 3 = -17 + 18
X x ( 18 - 3 ) = 1
X x 15 = 1
X = \(\frac{1}{15}\)
Vậy X = \(\frac{1}{15}\)
Tìm x biết (8*18-5*18-18*3)*x+2*x=8*7+24
(8*18-5*18-3*18)*x+2*x=8*7+24
\(\left(8\times18-5\times18-3\times18\right)\times x+2\times x=8\times7+24\)
\(18\times\left(8-5-3\right)\times x+2\times x=8\times7+24\)
\(0\times x+2\times x=8\times7+24\)
\(\left(0+2\right)\times x=8\times7+24\)
\(2\times x=8\times7+24\)
\(2\times x=56+24\)
\(2\times x=80\)
\(x=80:2\)
\(x=40\)
Tìm y biết :
(8 x 18 - 5 x 18 - 18 x 3) x y + 2 x y = 8 x 7 + 2
(8 x 18 -5 x 18 -18 x3) x y + 2 x y =8 x 7 + 2
<=>144 x y -90 x y -54 x y + 2 x y = 58
<=>2 x y = 58
<=> y = 29
Vậy y = 29
Tìm y biết :
(8 x 18 - 5 x 18 - 18 x 3) x y + 2 x y = 8 x 7 + 2
[ 18 x ( 8 - 5 - 3 ) ] x y = 56 + 2
[ 18 x ( 8 - 5 - 3 ) ] x y = 58
( 18 x 0 ) x y = 58
0 x y + 2 x y = 58
2 x y = 58
y = 58 : 2
y = 29
(8 x 18 - 5 x 18 - 18 x 3) x y + 2 x y
=[(8 - 5- 3) x 18] x y + 2 x y
=[0 x 18] x y + 2 x y
= 0 nhân cho bất kì số nào cũng bằng 0 nên chứng tỏ bài này cho sai đề
Cách làm nào đúng, cách làm nào sai
a) 24 : 6 :2 = 4 : 2 = 2
b) 24 : 6: 2 = 24 : 3 = 8
c) 18 : 3 x 2 = 18 : 6 = 3
d) 18 : 3 x 2 = 6 x 2 = 12
a) 24 : 6 : 2 = 4 : 2 = 2 => Đ
b) 24 : 6 : 2 = 24 : 3 = 8 => S
c) 18 : 3 x 2 = 18 : 6 = 3 => S
d) 18 : 3 x 2 = 6 x 2 = 12 => Đ
a, \(\dfrac{x-2}{15}+\dfrac{x-3}{14}+\dfrac{x-4}{13}+\dfrac{x-5}{12}=4\)
b, \(\dfrac{x+1}{19}+\dfrac{x+2}{18}+\dfrac{x+3}{17}+...+\dfrac{x+18}{2}+18=0\)
Cảm ơn khi đã giúp mình
a) Ta có: \(\dfrac{x-2}{15}+\dfrac{x-3}{14}+\dfrac{x-4}{13}+\dfrac{x-5}{12}=4\)
\(\Leftrightarrow\dfrac{x-2}{15}-1+\dfrac{x-3}{14}-1+\dfrac{x-4}{13}-1+\dfrac{x-5}{12}-1=0\)
\(\Leftrightarrow\dfrac{x-17}{15}+\dfrac{x-17}{14}+\dfrac{x-17}{13}+\dfrac{x-17}{12}=0\)
\(\Leftrightarrow\left(x-17\right)\left(\dfrac{1}{15}+\dfrac{1}{14}+\dfrac{1}{13}+\dfrac{1}{12}\right)=0\)
mà \(\dfrac{1}{15}+\dfrac{1}{14}+\dfrac{1}{13}+\dfrac{1}{12}>0\)
nên x-17=0
hay x=17
Vậy: x=17
b) Ta có: \(\dfrac{x+1}{19}+\dfrac{x+2}{18}+\dfrac{x+3}{17}+...+\dfrac{x+18}{2}+18=0\)
\(\Leftrightarrow\dfrac{x+1}{19}+1+\dfrac{x+2}{18}+1+\dfrac{x+3}{17}+1+...+\dfrac{x+18}{2}+1=0\)
\(\Leftrightarrow\dfrac{x+20}{19}+\dfrac{x+20}{18}+\dfrac{x+20}{17}+...+\dfrac{x+20}{2}=0\)
\(\Leftrightarrow\left(x+20\right)\left(\dfrac{1}{19}+\dfrac{1}{18}+\dfrac{1}{17}+...+\dfrac{1}{2}\right)=0\)
mà \(\dfrac{1}{19}+\dfrac{1}{18}+\dfrac{1}{17}+...+\dfrac{1}{2}>0\)
nên x+20=0
hay x=-20
Vậy: x=-20
Tính rồi so sánh kết quả: 18 : 3 và (18 x 4):(3 x 4)
18 : 3 = 6 ;
(18 x 4 ) : (3 x 4) = 73 : 12 = 6
Vậy kết quả của 18 : 3 và (18 x 4 ) : (3 x 4) bằng nhau
tìm x
(8x18 - 5x 18 - 18 x 3 ) x x + 2 x x = 8 x 7 +24
Đúng ghi Đ sai ghi S:
a,5 x 7/18 + 2/9 = 5 x 11/18=55/18
b,3/4 x (2/9+5/6) = 3/4 x 2/9 +3/4 x 5/6=1/6 + 5/8=19/24