Solve the simultaneous equations x^2 +8y=20 and y=x+4

To begin you must substitute the value of y provided into the first equation. The would change the equation into the following form:x^2+8(x+4)=20. Now expand the bracket so that the equation becomes:x^2+8x+32=20.Now subtract 20 from both sides to form a quadratic equationx^2+8x+12=0.Factorise the equation into (x+6)(x+2)=0 As 6 and 2 multiply to make 12 and add together to make 8. You can find all the factor pairs of twelve and check them to see if the add to make 8 in an exam to make sure there are no other possible answers. Since one of the two brackets must be equal to 0 x must be either -6 or -2 for this question. Substitute one of the values of x into the second equation provided.y=-6+4=-2. Therefore when x=-6, y=-2Repeat with the other value of x.y=-2+4=2. Therefore when x=-2, y-=2. In an exam remember to show your working as even if you come to the wrong answer you may still score some method marks which may boost your overall grade.

Answered by Anthony M. Maths tutor

2540 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

How do I solve a quadratic equation?


Shape ABCD is a parallelogram. Y is the mid-point of AB and Z is on BC such that BZ=1/2ZC. Given that AB=a and BC=b, describe, in terms of a and b: a) AC b)CY c)YZ


Solve the Simultaneous equations 4x - y = 8 and x + y = 12


How do you solve simultaneous equations?


We're here to help

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