Using a2−b2=(a+b)(a−b), find
1) 512−492
2) (1.02)2−(0.98)2
3) 1532−1472
4) 12.12−7.92
a2−b2=(a+b)(a−b) -Identity
1) 512−492=(51+49)(51−49)
=(100)×(2)
=200
2) (1.02)2−(0.98)2=(1.02+0.98)(1.02−0.98)
=(2)×(0.04)
=0.08
3) (153)2−(147)2=(153+147)(153−147)
=(300)×(6)
=1800
4) (12.1)2−(7.9)2=(12.1+7.9)(12.1−7.9)
=(20)×(4.2)
=84.