Question

ma ajuta cineva va roggg la mate nu inteleg

Answer 1

Ex 5
Fie a si b cele 2 numere
(1) a*b=72
Din (1)=>a*(b+10)=92=>a*b+a*10=92=>72+a*10=92=>
=> a*10=92-72=>a*10=20=> a=20/10=>a=2
Din a=2=>a*b=72=>2*b=72=>b=72/2=>b=36
Deci (a,b)={2,36}

ultimul ex
7*a+9*b+ 2*c=? daca a+b=43 si b+c=15
(1) b+c=15=>b=15-c
Din (1)=> a+b=43=>a=43-b=>a=43-(15-c)=>a= 43-15+c=>a= 28+c (2)
Din (1) si (2) => 7*a+9*b+ 2*c=7*(28+c)+9*(15-c)+2*c=>
=>7*a+9*b+ 2*c=7*28+7*c+9*15-9*c+2*c=>
=>7*a+9*b+ 2*c=7*28+9*15+(7*c-9*c+2*c)=>
=>7*a+9*b+ 2*c=196+135+ (-2*c+2*c)=>
=>7*a+9*b+ 2*c=196+135=>=>7*a+9*b+ 2*c=331