Question

By Factoring And Using Quadratic Formula x raise to two minus 10x is equals to negative 21

Answer 1

Answer:

$x =3$ or $x = 7$

Step-by-step explanation:

Given

$x^2 - 10x = -21$

Required

Solve by factoring & quadratic formula

By Factoring:

$x^2 - 10x = -21$

Equate to 0

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

Expand:

$x^2 - 7x -3x+21 = 0$

Factorize:

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

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

$x -3 = 0$ or $x - 7 = 0$

$x =3$ or $x = 7$

By quadratic

$x^2 - 10x = -21$

Equate to 0

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

For

$ax^2 + bx + c = 0$

x is solved using:

$x = \frac{-b\±\sqrt{b^2-4ac}}{2a}$

where

$a = 1$; $b = -10$; $c = 21$

So:

$x = \frac{-(-10)\±\sqrt{(-10)^2-4*1*21}}{2*1}$

$x = \frac{10\±\sqrt{100-84}}{2}$

$x = \frac{10\±\sqrt{16}}{2}$

$x = \frac{10\±4}{2}$

Split

$x = \frac{10+4}{2}$ or $x = \frac{10-4}{2}$

$x = \frac{14}{2}$ or $x = \frac{6}{2}$

$x = 7$ or $x =3$