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a) \(\left(a+b-c\right)-\left(b-c+d\right)\)
\(=a+b-c-b+c-d\)
\(=a+b-b-c+c-d\)
\(=a-d\)
b) \(-\left(a-b+c\right)+\left(a-b+d\right)\)
\(=\left(-a\right)+b-c+a+b-d\)
\(=\left(-a\right)+a+b+b-c-d\)
\(=2b-c-d\)
c) \(\left(a+b\right)-\left(-a+b-c\right)\)
\(=a+b+a-b+c\)
\(=a+a+b-b+c\)
\(=2a+c\)
d) \(-\left(a-b-c\right)+\left(a-b-c\right)\)
\(=-a+b+c+a+b+c\)
\(=-a+a+b+b+c+c\)
\(=2b+2c\)
(chắc hơi sai... > . < ...)
a) \(\left(a+b\right)\left(c+d\right)-\left(a+d\right)\left(b+c\right)\)
\(=ac+ad+bc+bd-ab-ac-db-dc\)
\(=ad+bc-dc-ab\)
\(=d\left(a-c\right)-b\left(a-c\right)\)
\(=\left(a-c\right)\left(d-b\right)\)
b) \(\left(a+b\right)\left(c-d\right)-\left(a-b\right)\left(c+d\right)\)
\(=ac-ad+bc-bd-ac-ad+bc+bd\)
\(=2bc-2ad\)
\(=2\left(bc-ad\right)\)
c) \(\left(a+b\right)^2-\left(a-b\right)^2\)
\(=\left(a+b\right)\left(a+b\right)-\left(a-b\right)\left(a-b\right)\)
\(=a^2+2ab+b^2-a^2+2ab-b^2\)
\(=4ab\)
a, -( -a + c - d) - ( c - d + d) = a - c + d - c + d - d = a + d
b, - ( a+b-c+d) + (a-b-c-d) = -a -b+c-d + a-b-c-d = -2b + (-2c)= -2(b+c)
a) = a(a+b) + b(a+b) = a2 +ab+ba+b2 = a2 +2ab+b2
b) = a(a-b) -b(a-b) = a2 -ab -ba +b2 = a2 - 2ab + b2
c) =a(a+b) - b(a+b) = a2 + ab - ab - b2 = a2 - b2
C = (a+b)(2+b)
= a(2+b) + b(2+b)
= 2a + ab + 2b + b2
D = (a-b)(a-b)
= a(a-b) - b(a-b)
= a2 - ab - ab + b2
= a2 - 2ab + b2
E = (a+b)(a-b)
= a(a-b) + b(a-b)
= a2 -ab + ba - b2
= a2 - b2.