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Simultaneous equations help needed please?
I'm confused with this question because there is a y and a y^2.
Could you help please?
y=2x-3
y^2=8x-16
1 Answer
- ?Lv 71 decade agoFavorite Answer
what is y^2: (2x-3)^2 = 4x^2-12x+9
plug that into second eqn:
4x^2-12x+9 = 8x -16
4x^2 -20x +25 =0
now this does not factor easily so I am going to take a different tact:
take first eqn and multiply by 4:
4y = 8x -12
solve for 8x: 8x = 4y+12
take second eqn and solve for 8x: 8x = y^2 +16
so y^2 +16 = 4y +12
y^2 -4y +4 =0
(y-2)*(y-2) = 0
implies y =2
check in first eqn: 2 = 2x -3
5/2 = x
plug (5/2, 2) into second eqn.
2^2 =? 8*5/2 -16
4 =? 20-16 yep it does!
ANSWER: x =5/2 (or equivalently y =2)
