1. ## Substitution Inequality

2x +3y = 5
x
² +3xy = 4

Okay, so I substitute y = -2/3x +5/3

x
² +3x(-2/3x +5/3) -4

I get '3x² +5x -4'

It doesn't factorise, so I use the formula and answers are decimals, but the answers in textbook are 1,1 and 4,-1

​So, what did I do wrong?

2. ## Re: Substitution Inequality

2x +3y = 5
x
² +3xy = 4

Okay, so I substitute y = -2/3x +5/3

x
² +3x(-2/3x +5/3) -4

I get '3x² +5x -4'

It doesn't factorise, so I use the formula and answers are decimals, but the answers in textbook are 1,1 and 4,-1

​So, what did I do wrong?
Check the coefficient of the x^2 again. x^2 - 2x^2 is....

-Dan

3. ## Re: Substitution Inequality

ffs. sorry. thanks.