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Mathematics

Solve the following equations by using formula:

x(3x+12)x \Big(3x + \dfrac{1}{2} \Big) = 6

Quadratic Equations

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Answer

The given equation is x(3x+12)x \Big(3x + \dfrac{1}{2} \Big) = 6

3x2+12x=66x2+x=126x2+x12=0\Rightarrow 3x^2 + \dfrac{1}{2}x = 6 \\[1em] \Rightarrow 6x^2 + x = 12 \\[1em] \Rightarrow 6x^2 + x - 12 = 0

Comparing it with ax2 + bx + c = 0
a= 6, b = 1, c = -12

By using the formula , x = b±b24ac2a\dfrac{-b ± \sqrt{b^2 - 4ac}}{2a} , we obtain

(1)±(1)24×6×122×61±1+288121+28912 or 1289121+1712 or 117121612 or 181243 or 32\Rightarrow \dfrac{-(1) ± \sqrt{(1)^2 - 4 \times 6 \times -12 }}{2 \times 6} \\[1em] \Rightarrow \dfrac{-1 ± \sqrt{1 + 288}}{12} \\[1em] \Rightarrow \dfrac{-1 + \sqrt{289}}{12} \text{ or } \dfrac{-1 - \sqrt{289}}{12} \\[1em] \Rightarrow \dfrac{-1 + 17}{12} \text{ or } \dfrac{-1 - 17}{12} \\[1em] \Rightarrow \dfrac{16}{12} \text{ or } -\dfrac{18}{12} \\[1em] \Rightarrow \dfrac{4}{3} \text{ or } -\dfrac{3}{2}

Hence, roots of the equation are 43,32\dfrac{4}{3} , -\dfrac{3}{2}.

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