Factorise Expression
1. Stating the problem: Factorise the expression $$7 - x^2 + 2(x - \sqrt{7})$$.
2. Expand the expression:
$$7 - x^2 + 2x - 2\sqrt{7}$$
3. Rearrange terms to group like terms:
$$-x^2 + 2x + (7 - 2\sqrt{7})$$
4. To factorise, rewrite the quadratic part in standard form:
$$-x^2 + 2x + (7 - 2\sqrt{7}) = -(x^2 - 2x - 7 + 2\sqrt{7})$$
5. Complete the square inside the parentheses:
$$x^2 - 2x = (x - 1)^2 - 1$$
So,
$$x^2 - 2x - 7 + 2\sqrt{7} = (x - 1)^2 - 1 - 7 + 2\sqrt{7} = (x - 1)^2 - 8 + 2\sqrt{7}$$
6. Simplify the constant term:
$$-8 + 2\sqrt{7}$$ does not factor nicely, so we write the expression as:
$$-( (x - 1)^2 - 8 + 2\sqrt{7} )$$
7. The expression is now factorised as much as possible:
$$-(x - 1)^2 + 8 - 2\sqrt{7}$$
Final answer: $$7 - x^2 + 2(x - \sqrt{7}) = -(x - 1)^2 + 8 - 2\sqrt{7}$$