Question

cho số abcd lấy a x 2 +5 x 5 +b x 10 + c x 10 + d - 2500 = abcd

Answer 1

Ta có : {[(2a+5)×5+b]×10+c}×10+d-2500={[10a+25+b]×10+c}×10+d-2500={100a+250+10b+c}×10+d-2500=1000a+2500+100b+10c+d-2500=1000a+100b+10c+d=abcd. Vậy {[(2a+5)×5+b]×10+c}×10+d-2500=abcd