Question

Using a² − b² = (a + b) (a − b), find

(i) 51² − 49² (ii) (1.02)² − (0.98)² (iii) 153² − 147²

(iv) 12.1² − 7.9²

Answer 1

(i) 51² − 49² = (51 + 49) (51 − 49)

= (100) (2) = 200

(ii) (1.02)² − (0.98)² = (1.02 + 0.98) (1.02 ­− 0.98)

= (2) (0.04) = 0.08

(iii) 153² − 147² = (153 + 147) (153 − 147)

= (300) (6) = 1800

(iv) 12.1² − 7.9² = (12.1 + 7.9) (12.1 − 7.9)

= (20.0) (4.2) = 84