Solve the simultaneous equations. 5x + y = 21 and x-3y = 9

Label the equations, [a] 5x + y =21 and [b] x-3y =9. [b]: x - 3y = 9, [c]: x = 3y + 9. Substitute [c] into [a] 5(3y + 9) + y = 21 , 16y + 45 = 21 16y = -24 , y = - 3/2. Substitute y = -3/2 into [b]: x + 9/2 = 9 , x = 9/2. Check answers: 5(9/2) + (-3/2) = 21 Yes , 9/2 - (-3/2) = 9 Yes.

Answered by Solomon K. Maths tutor

2074 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

I decrease a number by 26%, the answer is 9 x10^-7, what was the original number?


expand and simplify (x+4)(x-2)^2


Expand and simplify (m + 3)(m + 10)


Bob earns £7.70 an hour, and he works 30 hours per week. If Bob has 28 days of unpaid holidays to take, how much does he earn in a year? Also will he be taxed? (Bob will be taxed if he earns over £10000 in one year)


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2024

Terms & Conditions|Privacy Policy
Cookie Preferences