Question

calculati suma tuturor nr. de forma abba stiind ca ab-ba=3a+3b
Vă roggg !!!

Answer 1

ab-ba=3a+3b

10a+b-10b-a=3(a+b)

9a-9b=3(a+b)

9(a-b)=3(a+b)   |:3

3a-3b=a+b

3a-a=b+2b

2a=4b

a=2b =>b=1,2,3,4   ;a=2, 4, 6, 8

(a,b)={(2,1),(4,2),(6,3),(8,4)}

ab={21,42,63,84}

ba={12,42,36,48}

abba={(2112,4224,6336,8448}

suma=2112+4224+6336+8448=21120