Question

Tính nhanh a,999^2-1

b,101.99

c,117^2+17^2-234.17

Answer 1

a) 999² - 1 = 999² - 1² = (999 - 1).(999 + 1) = 998.1000 = 99800

b) 101.99 = (100+1).(100-1) = 100² - 1 = 10000 - 1 = 9999

Answer 2

a) 999² - 1

= 999² - 1² 

= (999+1)(999-1)

=1000.998 = 998000

b) 101.99=(100+1).99=100.99+1.99=9900+99=9999

c)117² +17² - 234.17

=117² + 17² - 117.2.17

=(117-17)² = 100² =10000

Answer 3

a. \(999^2-1=\left(999+1\right)\left(999-1\right)=1000.998=998000\)

b. \(101.99=\left(100+1\right)\left(100-1\right)=100^2-1=9999\)

c. \(117^2+17^2-234.17\\ =\left(117-17\right)^2=100^2=10000\)

Answer 4

a) \(999^2-1=\left(999-1\right)\left(999+1\right)=998\cdot1000=998000\)

b) \(101\cdot99=\left(100-1\right)\left(100+1\right)=100^2-1=10000-1=9999\)

c) \(117^2-234\cdot17+17^2=\left(117-17\right)^2=100^2=10000\)