How do you solve #3x² = 21#? Algebra Quadratic Equations and Functions Comparing Methods for Solving Quadratics 1 Answer Don't Memorise Jun 24, 2015 #color(green)( x = +sqrt7 # #color(green)( x = -sqrt7# Explanation: #3x² = 21# #3x² - 21=0# Here #3# is common to both terms: #3(x² - 7)=0# #x² - 7=0# #x² = 7# # x = +-sqrt7# The solutions are: #color(green)( x = +sqrt7 , x = -sqrt7# Answer link Related questions What are the different methods for solving quadratic equations? What would be the best method to solve #-3x^2+12x+1=0#? How do you solve #-4x^2+4x=9#? What are the two numbers if the product of two consecutive integers is 72? Which method do you use to solve the quadratic equation #81x^2+1=0#? How do you solve #-4x^2+4000x=0#? How do you solve for x in #x^2-6x+4=0#? How do you solve #x^2-6x-16=0# by factoring? How do you solve by factoring and using the principle of zero products #x^2 + 7x + 6 = 0#? How do you solve #x^2=2x#? See all questions in Comparing Methods for Solving Quadratics Impact of this question 3373 views around the world You can reuse this answer Creative Commons License