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36)Calculați numărul x stind ca a-b=6 si:
a)x+3×a-3×b=20
b)x×a-x×b+9a-9b=654
c)7×a-7×b+x=55
d)13+x-(5×a-5×b)=2011


Răspuns :

a)x+3×a-3×b=20
x+3(a-b)=20
x+3·6=20
x=20-18
x=2

b)x×a-x×b+9a-9b=654
x(a-b)+9(a-b)=654
(a-b)(x+9)=654
6(x+9)=654
x+9=654/6
x+9=109
x=109-9
x=100

c)7×a-7×b+x=55
7(a-b)+x=55
7·6+x=55
x=55-42
x=13

d)13+x-(5×a-5×b)=2011
13+x-5(a-b)=2011
x-5
··6=2011-13
x-30=1998
x=1998+30
x=2028