Question

factorise x²-10x+21​

Answer 1

Given equation

$x^{2} -10x+21=0$

Solving, we get,

$x^{2} -10x+21=0$

$\implies x^{2} -3x-7x+21=0$

$\implies x(x-3)-7(x-3)=0$

$\implies (x-7)(x-3)=0$

Now,

$x-7=0\\\implies x = 7\\\\x-3=0\\\implies x = 3$

$\boxed{\boxed{\bold{Therefore, \ the \ factorised \ expression \ is \ (x-7)(x-3)}}}}}}}}}}}$

                                                                             

Answer 2

★ Solution :

$:\implies\sf x^2 - 10x + 21 = 0 \\\\\\:\implies\sf x^2 - 7x - 3x + 21 = 0\\\\\\:\implies\sf x \big\{ x - 7 \big\} - 3\big\{x - 3\big\} = 0\\\\\\:\implies\sf \big\{x - 3\big\} \big\{ x - 7\big\} = 0$

Therefore,

$\begin{lgathered}\bullet\:\:\textsf{x - 3 = 0 = \textbf{x = 3}}\\\bullet\:\:\textsf{ x - 7 = 0 = \textbf{x = 7}}\end{lgathered}$