Answer:
[tex]x =3[/tex] or [tex]x = 7[/tex]
Step-by-step explanation:
Given
[tex]x^2 - 10x = -21[/tex]
Required
Solve by factoring & quadratic formula
By Factoring:
[tex]x^2 - 10x = -21[/tex]
Equate to 0
[tex]x^2 - 10x +21 = 0[/tex]
Expand:
[tex]x^2 - 7x -3x+21 = 0[/tex]
Factorize:
[tex]x(x-7)-3(x-7) = 0[/tex]
[tex](x-3)(x-7) = 0[/tex]
[tex]x -3 = 0[/tex] or [tex]x - 7 = 0[/tex]
[tex]x =3[/tex] or [tex]x = 7[/tex]
By quadratic
[tex]x^2 - 10x = -21[/tex]
Equate to 0
[tex]x^2 - 10x +21 = 0[/tex]
For
[tex]ax^2 + bx + c = 0[/tex]
x is solved using:
[tex]x = \frac{-b\±\sqrt{b^2-4ac}}{2a}[/tex]
where
[tex]a = 1[/tex]; [tex]b = -10[/tex]; [tex]c = 21[/tex]
So:
[tex]x = \frac{-(-10)\±\sqrt{(-10)^2-4*1*21}}{2*1}[/tex]
[tex]x = \frac{10\±\sqrt{100-84}}{2}[/tex]
[tex]x = \frac{10\±\sqrt{16}}{2}[/tex]
[tex]x = \frac{10\±4}{2}[/tex]
Split
[tex]x = \frac{10+4}{2}[/tex] or [tex]x = \frac{10-4}{2}[/tex]
[tex]x = \frac{14}{2}[/tex] or [tex]x = \frac{6}{2}[/tex]
[tex]x = 7[/tex] or [tex]x =3[/tex]
