Question

evaluate: (105)^2-(104)^2 / (6)^2-(5)^2

Answer 1

using a^2-b^2=(a+b)(a-b)
=(105+104)(105-104)/(6+5)(6-5)
=209*1/11*1
=19

Answer 2

${105}^{2} - {104}^{2} \div {6}^{2} - {5}^{2} \\ = (105 + 104)(105 - 104) \div( 6 + 5)(6 - 5) \\ = 209 \times 1 \div 11 \times 1 \\= \frac{209}{11} \\ =19$