Question
Solve equation using factorisation method $:(x +1)(2x + 8) = (x + 7)(x +3)$
✓
Answer
$(x +1)(2x + 8) = (x + 7)(x +3)$
$\Rightarrow 2x^2 + 8x + 2x + 8 = x2 + 3x + 7x + 21$
$\Rightarrow 2x^2 + 10x + 8 =x^2 + 10x + 21$
$\Rightarrow x2 - 13 =0$
$\Rightarrow x^2-(\sqrt{13})^2=0$
$\Rightarrow(x+\sqrt{13})(x-\sqrt{13})=0$
$\text { If } x+\sqrt{13}=0 \text { or } x-\sqrt{13}=0$
$\Rightarrow x=-\sqrt{13} \text { or } x=\sqrt{13}$
$\Rightarrow 2x^2 + 8x + 2x + 8 = x2 + 3x + 7x + 21$
$\Rightarrow 2x^2 + 10x + 8 =x^2 + 10x + 21$
$\Rightarrow x2 - 13 =0$
$\Rightarrow x^2-(\sqrt{13})^2=0$
$\Rightarrow(x+\sqrt{13})(x-\sqrt{13})=0$
$\text { If } x+\sqrt{13}=0 \text { or } x-\sqrt{13}=0$
$\Rightarrow x=-\sqrt{13} \text { or } x=\sqrt{13}$
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