Simplify $3 a^{2} (5 a^{2} - 3 a - 24)$ and also find its value for

(i) a = 1 (ii) a = 2. [3 MARKS]

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Solution

Simplification: 1 Mark
Substitution: 1 Mark each

$3 a^{2} (5 a^{2} - 3 a - 24) = 15 a^{4} - 9 a^{3} - 72 a^{2}$

$(i) a = 1$

$\Rightarrow 15 (1)^{4} - 9 (1)^{3} - 72 (1)^{2}$

$= 15 (1) - 9 (1) - 72 (1)$

$= - 66$

$(i i) a = 2$

$\Rightarrow 15 (2)^{4} - 9 (2)^{3} - 72 (2)^{2}$

$= 15 (16) - 9 (8) - 72 (4)$

$= 240 - 72 - 288$

$= - 120$

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Similar questions

3 a^{2} (5 a^{2} - 3 a - 24)

3 x (4 x - 5) + 3

x = 3

x = \frac{1}{2}

a (a^{2} + a + 1) + 5

a = 0

a = 1

a = - 1

(a) Simplify 3x (4x −5) + 3 and find its values for (i) x = 3, (ii) .

(b) a (a² + a + 1) + 5 and find its values for (i) a = 0, (ii) a = 1, (iii) a = − 1.

3 x (4 x - 5) + 3

x = 3

x = \frac{1}{2}

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