Solve the simultaneous equations: 5x+y=21, x-3y=9
Step 1. Take one equation and make either x or y the subject of the formulax=9+3y, 5x+y=21Step 2. Substitute in the equation5(9+3y)+y=21Step 3. Make y the subject of the formula45+15y+y=21 (multiplied out the brackets)16y=-24 (Subtracted 45 from both sides)y=-24/16 (Divided by 16 on both sides)y=-3/2 (Scaled the fraction down) Step 4. Find out what x is equal tox=9+3(-3/2)x=4.5 or 9/2
MJ
Related Maths GCSE answers
All answers ▸Tommy, Anna and Jacob all have 40 sweets. they decide to split the sweets between each other in the ratio 1:4:5. Calculate how many sweets each get, rounding down your answer where necessary.
How can I find x and y?
Calculate the diameter of a circle with area 80cm^2 to two significant figures.
what is the point of intersection between the lines 3y-4x=12 and 2x=2y+3