Question

Evaluate the following using suitable identities: 
(i) (99)3
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Answer 1

$\huge\red{ⓐⓝⓢⓦⓔⓡ}$

We can write 99 as 100–1

Using identity,

$(x –y)^3 = x^3–y^3–3xy(x–y)$

$(99)^3 = (100–1)^3$

$= (100)^3–13–(3×100×1)(100–1)$

$= 1000000 –1–300(100 – 1)$

$= 1000000–1–30000+300$

$= 970299$

Answer 2

Ionic compounds have high melting points. Ionic compounds are hard and brittle. Ionic compounds dissociate into ions when dissolved in water. Solutions of ionic compounds and melted ionic compounds conduct electricity, but solid materials do not