Q5 of 157 Page 22

Evaluate the following by using the identities:
28 × 32

Answer: 896

∵ 28 × 32= (30 – 2) (30 + 2)

We know that

∵ (a² – b²) = (a – b) × (a + b)

∴ (30 – 2) (30 + 2) = (30)² – (2)²

⇒ (30 – 2) (30 + 2) = 900 – 4 = 896

Evaluate the following by using the identities:

53 × 47

Evaluate the following by using the identities:

96 × 104

Evaluate the following by using the identities:

81 × 79

Evaluate the following by using the identities:

2.8²

Questions · 157

1. Algebra

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Evaluate the following by using the identities:28 × 32Answer: 896