x^2-10x=21

Question

this is so supposed to be solved by graphing but i know you can't do that here so pls help regardless 

Answer 1

You can solve using the quadratic formula.

 

x² - 10x - 21 = 0

 

a = 1

b = -10

c = -21

 

x= (1/2a)[-b ± √(b² - 4ac)] = (1/2)[10 ± √(100 + 84)] = 5 ± √46

Answer 2

x² - 10x = 21

x² - 10x + 25 = 21 + 25    complete the square

(x - 5)² = 46

x - 5 = ±√46

x = 5 ± √46