Question

Simplify 3x(4x-5)+3 and find its
value for (i)x= 3 (ii) X = 1/2​

Answer 1

Answer:

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Step-by-step explanation:

$3x(4x-5)+3 \\ 12 {x}^{2} - 15x + 3 \\ - - - - - - - - \\ when \: \: x = 3 \\ 12(3) {}^{2} + 15(3) + 3 \\ 12(9) + 45 + 3 \\ 108 + 45 + 3 \\ 156 \\ - - - - - - - - \\ when \: \: x = \frac{1}{2} \\ \\ 12( \frac{1}{2} ) {}^{2} + 15( \frac{1}{2} ) + 3 \\ \\ 12( \frac{1}{4} ) + \frac{15}{2} + 3 \\ \\ \frac{12}{4} + \frac{15}{2} + 3 \\ \\ 3 + \frac{15}{2} + 3 \\ \\ 6 + \frac{15}{2} \\ \\ taking \: \: lcm \\ \\ \frac{6 \times 2}{1 \times 2} + \frac{15}{2} \\ \\ \frac{12}{2} + \frac{15}{2} \\ \\ \frac{12 + 15}{2} \\ \\ \frac{27}{2}$

Answer 2

:

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3x(4x−5)+3=12x^2−15x+3

x=3 gives the value 12(9)−15×3+3

                             =108−45+3

                              =66

x=1/2 gives the value 12(1/4)−15×(1/2)+3

                             =3−7.5+3

                              = - 3/2