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Mathematics

Solve the following equation by factorisation:

23x213x=1\dfrac{2}{3}x^2 - \dfrac{1}{3}x = 1

Quadratic Equations

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Answer

Given,

23x213x=123x213x1=0 (Writing as ax2+bx+c=0)23x2×313x×31×3=0×3 (Multiplying the equation by 3) 2x2x3=02x23x+2x3=0x(2x3)+1(2x3)=0(x+1)(2x3)=0 (Factorising left side) x+1=0 or 2x3=0 (Zero-product rule) x=1 or x=32\dfrac{2}{3}x^2 - \dfrac{1}{3}x = 1 \\[1em] \Rightarrow \dfrac{2}{3}x^2 - \dfrac{1}{3}x - 1 = 0 \text{ (Writing as } ax^2 + bx + c = 0) \\[1em] \Rightarrow \dfrac{2}{3}x^2 \times 3 - \dfrac{1}{3}x \times 3 - 1 \times 3 = 0 \times 3 \text{ (Multiplying the equation by 3) } \\[1em] \Rightarrow 2x^2 - x - 3 = 0 \\[1em] \Rightarrow 2x^2 - 3x + 2x - 3 = 0 \\[1em] \Rightarrow x(2x - 3) + 1(2x - 3) = 0 \\[1em] \Rightarrow (x + 1)(2x - 3) = 0 \text{ (Factorising left side) } \\[1em] \Rightarrow x + 1 = 0 \text{ or } 2x - 3 = 0 \text{ (Zero-product rule) } \\[1em] \Rightarrow x = -1 \text{ or } x = \dfrac{3}{2}

Hence, the roots of given equation are -1, 32\dfrac{3}{2}.

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