How do you solve #x^2+y^2=153, y=-4x#? Precalculus Solving Systems of Two Equations Solving by Substitution 1 Answer ali ergin Dec 10, 2016 #x={-3,+3}# Explanation: #x^2+y^2=153# #y=-4x# #(y^2)=(-4)^2# #(y)^2=16x^2# #x^2+16x^2=153# #17x^2=153# #x^2=153/17# #x^2=9# #x={-3,+3}# Answer link Related questions What is a system of equations? What does it mean to solve a system of equations by substitution? How do I use substitution to find the solution of the system of equations #c+3d=8# and #c=4d-6#? How do you write a system of linear equations in two variables? How does a system of linear equations have no solution? How many solutions can a system of linear equations have? What is the final step of completing a solve by substitution problem? How do I use substitution to find the solution of the system of equations #4x+3y=7# and #3x+5y=8#? How do I use substitution to find the solution of the system of equations #y=2x+1# and #2y=4x+2#? How do I use substitution to find the solution of the system of equations #y=1/3x+7/3# and... See all questions in Solving by Substitution Impact of this question 6542 views around the world You can reuse this answer Creative Commons License