Bài 3: Thu gọn các biểu thức:
a) A=(2a+b+3c)-(a-b+c)
b) B= (a+b-c)-(a-b+c)-(a-b-c)
c) C=(a-2b-c)-(-2a+b-c)-(-a-b-2c)
Câu 1. Khai triển các biểu thức:
a) (a-b+c)2 b) (a+2b-c)2
c) (2a-b-c)2
Câu 2. Rút gọn biểu thức:
a) A=(x-y)2+(x+y)2
b) B=(2x-1)2-2(2x-3)2+4
Câu 3. Tính nhanh:
a) 492 b) 512
c) 99.100
Câu 4. Tìm x, biết:
a) 16x2-(4x-5)2=15 b) (2x+1)(1-2x)+(1-2x)2=18
c) (x-5)2-x(x-4)=9 d) (x-5)2+(x-4)(1-x)=0
Tách ra mỗi câu một lần.
Dài quá không ai làm đâu.
Nhìn nản lắm.
Câu 3:
a: \(49^2=2401\)
b: \(51^2=2601\)
c: \(99\cdot100=9900\)
Khai triển các biểu thức:
a) (a-b+c)2 b) (a+2b-c)2
c) (2a-b-c)2
a, \(\left(a-b+c\right)^2=a^2+b^2+c^2-2ab-2bc+2ca\)
b, \(\left(a+2b-c\right)^2=a^2+4b^2+c^2+4ab-4bc-2ca\)
c, \(\left(2a-b-c\right)^2=4a^2+b^2+c^2-4ab+2bc-4ca\)
rút gọn theo quy tắc đấu ngoặc
A =(a+b-2c) -(-a+b+c) -(2a-b-c)
B=-(2a-b+c) + (b-2c-3a) -(-5a-3c+b)
C=(3a-b-2c)-( 2b+3c-a) +(2a-3b)
D=(5a-3b+c) +( 2a-3b+5) -( b-c+a)
A =(a+b-2c) -(-a+b+c) -(2a-b-c)
= a+b-2c+a-b-c-2a+b+c
= b-2c
B=-(2a-b+c) + (b-2c-3a) -(-5a-3c+b)
= -2a+b-c+b-2c-3a+5a+3c-b
= b-c
C=(3a-b-2c)-( 2b+3c-a) +(2a-3b)
= a-b-2c-2b-3c+a+2a-3b
= -6b-5c
D=(5a-3b+c) +( 2a-3b+5) -( b-c+a)
= 5a-3b+c+2a-3b+5-b+c-a
= 6a-7b+2c
\(A=\left(a+b-2c\right)-\left(-a+b+c\right)-\left(2a-b-c\right)\)
\(=a+b-2c+a-b-c-2a+b+c=b-2c\)
\(B=-\left(2a-b+c\right)+\left(b-2c-3a\right)-\left(-5a-3c+b\right)\)
\(=-2a+b-c+b-2c-3a+5a+3c-b=b\)
\(C=\left(3a-b-2c\right)-\left(2b+3c-a\right)+\left(2a-3b\right)\)
\(=3a-b-2c-2b-3c+a+2a-3b=6a-6b-5c\)
\(D=\left(5a-3b+c\right)+\left(2a-3b+5\right)-\left(b-c+a\right)\)
\(=5a-3b+c+2a-3b+5-b+c-a=6a-7b+2c\)
Phá ngoặc rồi viết gọn
1 , a - ( a - b - c ) - ( b - c -a ) - ( c - b -a )
2 , - ( a + b + c ) - ( b - c -a ) + ( 1 - a - b ) - ( c - 3b )
3 , ( b - c - 6 ) - ( 7 - a + b ) + c
4 , - ( 3b - 2a - c ) - ( a - b - c ) - ( a - 2b -+ 2c )
5 , ( 4a - 3b + 2c ) - ( 4b - 3c - 2a ) - ( 4c - 3a + 2b ) + ( a - b ) - c
6, 2a - { a - b [ a - b - ( a + b + c ) + 2b ] - c - b }
Phá ngoặc rồi viết gọn
1 , a - ( a - b - c ) - ( b - c -a ) - ( c - b -a )
2 , - ( a + b + c ) - ( b - c -a ) + ( 1 - a - b ) - ( c - 3b )
3 , ( b - c - 6 ) - ( 7 - a + b ) + c
4 , - ( 3b - 2a - c ) - ( a - b - c ) - ( a - 2b -+ 2c )
5 , ( 4a - 3b + 2c ) - ( 4b - 3c - 2a ) - ( 4c - 3a + 2b ) + ( a - b ) - c
6, 2a - { a - b [ a - b - ( a + b + c ) + 2b ] - c - b }
1 , a - ( a - b - c ) - ( b - c -a ) - ( c - b -a )
= a - a + b + c - b + c + a - c + b + a
= (a-a+a) + (b-b+b) + (c-c+c)
= a+b+c
2 , - ( a + b + c ) - ( b - c -a ) + ( 1 - a - b ) - ( c - 3b )
= -a - b - c - b + c + a + 1 - a - b - c + 3b
= (a+a-a) - (b+b+b) + (c-c+c) + 3b
= a - 3b + c + 3b
= a+c + (3b - 3b)
= a+c + 0
= a+c
3 , ( b - c - 6 ) - ( 7 - a + b ) + c
= b - c - 6 - 7 + a - b + c
= (b-b) + (c-c) - (6+7) + a
= 0 + 0 - 13 + a
= -13 + a
4 , - ( 3b - 2a - c ) - ( a - b - c ) - ( a - 2b -+ 2c )
= -3b + 2a + c - a + b + c - a + 2b - 2c
= -3b + (2b + b) + (c + c) - (a+a) +2a - 2c
= -3b + 3b + 2c - 2a + 2a - 2c
= (3b - 3b) + (2c - 2c) + (2a + 2a)
= 0 + 0 + 0
= 0
chỉ bt lm đến đây thoy
i-------------7jhmnjbn,j,mn.kmlk.jk,hkghnmgvbvcbvcbcvbcvbcbbccbcbcb
Phá ngoặc rồi viết gọn
1 , a - ( a - b - c ) - ( b - c -a ) - ( c - b -a )
2 , - ( a + b + c ) - ( b - c -a ) + ( 1 - a - b ) - ( c - 3b )
3 , ( b - c - 6 ) - ( 7 - a + b ) + c
4 , - ( 3b - 2a - c ) - ( a - b - c ) - ( a - 2b -+ 2c )
5 , ( 4a - 3b + 2c ) - ( 4b - 3c - 2a ) - ( 4c - 3a + 2b ) + ( a - b ) - c
6, 2a - { a - b [ a - b - ( a + b + c ) + 2b ] - c - b }
giúp mình đi mình xin các bạn cần gấp lắm !!
2, - ( a + b + c ) - ( b - c -a ) + ( 1 - a - b ) - ( c - 3b )
= -a - b -c - b + c + a + 1 - a - b - c + 3b
= (a-a) - (b+b+b) + (c-c) + (-a) + (-c) + 3b
= 0 - 3b + 0 + (-a) + (-c) + 3b
= (3b-3b) + (-a) + (-c)
= 0 + (-a) + (-c)
= (-a) + (-c)
3, ( b - c - 6 ) - ( 7 - a + b ) + c
= b - c - 6 - 7 + a - b + c
= (b-b) + (c-c) - (6+7) + a
= 0 + 0 + 13 + a
= 13 + a
6, 2a - { a - b [ a - b - ( a + b + c ) + 2b ] - c - b }
= 2a - { a - b [ a - b - a - b - c + 2b ] - c - b }
= 2a - { a - b [ ( a - a ) - (b+b) - c + 2b ] - c - b }
= 2a - { a - b [ 0 - 0 - 2b - c + 2b ] - c - b }
= 2a - { a- b [ (2b - 2b) - c ] - c - b }
= 2a - { a - b [ 0 - c ] - c - b }
= 2a - { a - b.(-c) - c - b}
= 2a - a - b.(-c) - c - b
= 1a - (-b).c - c - b
= a - (-b).c - c.1 - b
= a - [(-b) - 1].c - b
ko chắc lắm
Phá ngoặc rồi viết gọn
1 , a - ( a - b - c ) - ( b - c -a ) - ( c - b -a )
2 , - ( a + b + c ) - ( b - c -a ) + ( 1 - a - b ) - ( c - 3b )
3 , ( b - c - 6 ) - ( 7 - a + b ) + c
4 , - ( 3b - 2a - c ) - ( a - b - c ) - ( a - 2b -+ 2c )
5 , ( 4a - 3b + 2c ) - ( 4b - 3c - 2a ) - ( 4c - 3a + 2b ) + ( a - b ) - c
6, 2a - { a - b [ a - b - ( a + b + c ) + 2b ] - c - b }
1) a - ( a - b - c ) - ( b - c - a ) - ( c - b - a )
= a - a + b + c - b + c + a - c + b + a
= 2a + b + c
2) - ( a + b + c ) - ( b - c - a ) + ( 1 - a - b ) - ( c - 3b )
= -a - b - c - b + c + a + 1 - a - b - c + 3b
= 1 - a - c
1,a-(a-b-c)-(b-c-a)-(c-b-a)
=a-a+b+c-b+c+a-c+b+a
=2a+b+c
2,-(a+b+c)-(b-c-a)+(1-a-b)-(c-3b)
=-a-b-c-b+c+a+1-a-b-c+3b
=1-a-c
3,(b-c-6)-(7-a+b)+c
=b-c-6-7+a-b+c
=a-13
4,-(3b-2a-c)-(a-b-c)-(a-2b+2c)
=-3b+2a+c-a+b+c-a+2b-2c
=0
5,(4a-3b+2c)-(4b-3c-2a)-(4c-3a+2b)+(a-b)-c
=4a-3b+2c-4b+3c+2a-4c+3a-2b+a-b-c
=(4a+2a+3a+a)-(3b+4b+2b+b)+(2c+3c-4c-c)
=10a-10b+0
=10.(a-b)
6,
2a-{a-b[a-b-(a+b+c)+2b]-c-b}
=2a-{a-b[a-b-a-b-c+2b]-c-b}
=2a-a-bc+c+b
=a-bc+c+b
=(a+b)-b(c-1)
Phá ngoặc rồi viết gọn
1 , a - ( a - b - c ) - ( b - c -a ) - ( c - b -a )
2 , - ( a + b + c ) - ( b - c -a ) + ( 1 - a - b ) - ( c - 3b )
3 , ( b - c - 6 ) - ( 7 - a + b ) + c
4 , - ( 3b - 2a - c ) - ( a - b - c ) - ( a - 2b -+ 2c )
5 , ( 4a - 3b + 2c ) - ( 4b - 3c - 2a ) - ( 4c - 3a + 2b ) + ( a - b ) - c
6, 2a - { a - b [ a - b - ( a + b + c ) + 2b ] - c - b }
a - ( a - b - c ) - ( b - c - a ) - ( c - b - a)
= a - a + b + c - b + c + a - c + b + a
= ( a -a + a ) + ( b - b + b ) + ( c + c - c) ( vì mình ko có ngoặc vuông nên chỉ thế này thôi)
= a + b + c
Bạn tự làm hết nha
1)=>a-a+b+b-b+c+a-c+b+a=2a+2b+c=2(a+b)+c
2)=>-a-b-c-b+c+a+1-a-b-c+3b=-a
3)=>b-c-6-7+a-b+c=-13+a
4)-3b+2a+c-a+b+c-a+2b-2c=0
5)=>4a-3b+2c-4b+3c+2a-4c+3a-2b+a-b-c=-2a-10b-2c
2a - { a - b [ a - b - ( a + b + c ) + 2b ] - c - b }
=2a-{a-b[a-b-a-b-c+2b]-c-b}
=2a-{a-bc-c-b}
=2a-a-bc-c-b
=a-bc-b-c
Cho 3 số dương a,b,c thỏa măn 2a+b-c/c = 2b+c-a/a = 2c+a-b/b
Tính A= (3a-c)(3b-a)(3c-b)/(3a-2b)(3b-2c)(3c-2a)