Question

tìm các số nguyên a,b,c,d biết:

a+b+c+d=1

a+c+d=2

a+b+d=3

a+b+c=4

Answer 1

Ta có: (a+b+c+d)-(a+c+b)=1-2

=>b=-1

          (a+b+c+d)-(a+b+d)=1-3

=>c=-2

          (a+b+c+d)-(a+b+c)=1-4

=>d=-3

          a+b+c+d=1

=>a+(-1)+(-2)+(-3)=1

=>a+(-6)=1

=>a=1-(-6)

=>a=7

Vậy a=7,b=-1,c=-2,d=-3

Answer 2

b=1-2=-1

c=1-3=-2

d=1-4=-3

a = 1-(-1)-(-2)-(-3) =7

Answer 3

Ta có: 
\(b=\left(a+b+c+d\right)-\left(a+c+d\right)\Rightarrow b=1-2=-1\)
\(c=\left(a+b+c+d\right)-\left(a+b+d\right)\Rightarrow c=1-3=-2\)
\(d=\left(a+b+c+d\right)-\left(a+b+c\right)\Rightarrow d=1-4=-3\)
\(a+-1+-2+-3=1\Rightarrow a=1-\left(-3\right)-\left(-2\right)-\left(-1\right)=7\)

Answer 4

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Answer 5

a+c+d=2