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Mathematics

Using standard formulae, expand each of the following:

(i) (4a + 9)2

(ii) (3x + 10y)2

(iii) (2m+3n)2(\sqrt{2}m + \sqrt{3}n)^2

Expansions

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Answer

We know that,

⇒ (a + b)2 = a2 + b2 + 2ab.

(i) Given,

⇒ (4a + 9)2

⇒ (4a)2 + (9)2 + 2 × 4a × 9

⇒ 16a2 + 81 + 72a.

Hence, (4a + 9)2 = 16a2 + 81 + 72a.

(ii) Given,

⇒ (3x + 10y)2

⇒ (3x)2 + (10y)2 + 2 × 3x × 10y

⇒ 9x2 + 100y2 + 60xy.

Hence, (3x + 10y)2 = 9x2 + 100y2 + 60xy.

(iii) Given,

(2m+3n)2(2m)2+(3n)2+2×2m×3n2m2+3n2+26mn.\Rightarrow (\sqrt{2}m + \sqrt{3}n)^2 \\[1em] \Rightarrow (\sqrt{2}m)^2 + (\sqrt{3}n)^2 + 2 \times \sqrt{2}m \times \sqrt{3}n \\[1em] \Rightarrow 2m^2 + 3n^2 + 2\sqrt{6}mn.

Hence, (2m+3n)2=2m2+3n2+26mn(\sqrt{2}m + \sqrt{3}n)^2 = 2m^2 + 3n^2 + 2\sqrt{6}mn.

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