### Home > PC > Chapter 6 > Lesson 6.2.1 > Problem6-75

6-75.

Solve the following equations.

1. $x^{2} − 4x = 21$

1. Set everything $= 0$
2. Factor or use the quadratic formula.
3. How many answers should you have?

1. $3 + \frac { 1 } { x } = \frac { 10 } { x ^ { 2 } }$

Set the entire function $= 0$.

1. $\left(x − 2\right)\left(x + 1\right) = 4$

Multiply each term by $x^{2}$.

1. $\sqrt { 6 x ^ { 2 } + 5 x } = 5$

Square both sides first.