tinh bang cach thuan tien :
1/1x4 + 1/4x 7 + 1/7 x 10 + . . . 1/ 97 x 100
10 nguoi dau tien xong truoc mik tik cho , nho trinh bay
tinh bang cach thuan tien 3/5 x 7/9 + 11/9 x 3/5 - 3/10. B 14/13 : 1/2 + 3/13 x2 -2 x 7/13
a) 3/5x7/9+11/9x3/5
=3/5 x(7/9+11/9)
= 3/5x2
=6/5
b)14/13:1/2+3/13x2-2x7/13
= 14/13 x 2 +3/13 x2 - 2x7/13
=2 x (14/13 +3/13 -7/13)
= 2 x 10/13
= 20/13
a) 3/5 x 7/9 + 11/9 x 3/5 - 3/10
= 3/5 x 7/9 + 11/9 x 3/5 - 3/5 x 2
= 3/5 x ( 7/9 + 11/9 - 2 )
= 3/5 x 0
= 0
b) 14/13 : 1/2 + 3/13 x 2 - 2 x 7/13
= 14/13 x 2/1 + 3/13 x 2 - 2 x 7/13
= ( 14/13 + 3/13 - 7/13 ) x 2
= 10/13 x 2 = 20/13
chẳng hiể gì cả
( 5 + 10 + 15 + 20 + 25 + 30 + 35 ) x ( 42 - 6 x 7 )
tinh bang cach thuan tien nhat
( 5 + 10 + 15 + 20 + 25 + 30 + 35 ) x ( 42 - 6 x 7 )
= ( 5 + 10 + 15 + 20 + 25 + 30 + 35 ) x ( 42 - 42 )
= ( 5 + 10 + 15 + 20 + 25 + 30 + 35 ) x 0
= 0
tinh bang cach thuan tien:
3/5+4/7+2/5+1/7+2/7=
\((\frac{3}{5}+\frac{2}{5})+(\frac{4}{7}+\frac{1}{7}+\frac{2}{7})\) ) =1+1=2
tinh bang cach thuan tien
7 / 19 * 1 /3 + 7 / 19 * 2 / 3
=\(\frac{7}{19}\) * \(\left(\frac{1}{3}+\frac{2}{3}\right)\)
=\(\frac{7}{19}\)* \(1\)
=\(\frac{7}{19}\)
Thế đó,đơn giản dzậy thôi!!!GOOD LUCK !!!
7 / 19 * 1 / 3 + 7 / 19 * 2 / 3
= 7 / 19 * ( 1 / 3 + 2 / 3 )
= 7 / 19 * 1
= 7/ 19
Bai1 .tim x : [ x nho la dau nhan , X la so can tim ]
3/5 + 2/7 : X = 1
2,04 : [ X + 6/5 ] =0,2
9,15 x X + 2,85 x X = 48
53,2 : [ X - 3,5 ] + 45,8 = 99
nho trinh bay ai xong truoc tui tik xcho
2/7:x=1-2/7
2/7:x=2/5
x=2/7:2/5
x=5/7
x+6/5=2,04:0,2
x+6/5=51/5
x=51/5-6/5
x=9
tinh bang cach thuan tien nhat : 3/4 x 4/5 + 5/6 x 6/7 x 7/8
1+2+3+4+5+6+7+8+9
tinh bang cach thuan tien nhat
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9
= (1 + 9) + (2 + 8) + (3 + 7) + (4 + 6) +5
= 10 + 10 + 10 +10 + 5
= 10 x 4 + 5
= 40 + 5
= 45
1+2+3+4+5+6+7+8+9
=[1+9]+[2+8]+[3+7]+[4+6]+5
=10+10+10+10+5
=40+5
=45
Tinh gia tri bieu thuc bang cach thuan tien nhat :
A= 1/10 x 2/9 x 3/8 x 4/7 x 5/6 x 6/5 x 7/4 x 8/3 x 9/2
tinh bang cach thuan tien nhat a.3/5+4/7+2/5+1/7+2/7 b.1/3+1/6+4/3+2/6+2/3