O-Level Additional Math

[Jtutor]

Hi jovially,


I’m back and have just forwarded you the compilation for your reference.
Hope you will find it useful for your child.

Cheers!
Jtutor

[Herbie]

xy+y+2= 0 and 2x+9y-30. Can advise how ro solve this simult eqn? Tq

[koguma]

Herbie:

xy+y+2= 0 and 2x+9y-30. Can advise how ro solve this simult eqn? Tq

Is there a typo error in the second equation \"2x+9y-30\" ???
Should it be \"2x+9y=30\" ??

If yes, from this equation, makes x the subject,
i.e. x = (30-9y) / 2

Then subsitute x = (30-9y) / 2 into \"xy+y+2= 0\".

[Herbie]

Sorry, part 2 of the qn shld be 2x+9y-3=0

[Herbie]

Sorry, part 2 of the qn shld be 2x+9y-3=0

[Herbie]

xy+y+2= 0 and 2x+9y-30. Can advise how ro solve this simult eqn? Tq

[koguma]

Herbie:

xy+y+2= 0 and 2x+9y-30. Can advise how ro solve this simult eqn? Tq

Think more you type, more you confuse on the part 2
Assume the 2 equations are
xy+y+2= 0 -- (1)
2x+9y-3=0 -- (2)

From (2), make x the subject,
2x = 3-9y
x = (3-9y) / 2 -- (3)

Put (3) into (2),
[(3-9y) / 2][y] + y +2 =0
[(3y-9y^2 ) /2 ]+y +2 = 0
3y - 9y^2 +2y +4 = 0
9y^2 - 5y - 4 =0
(9y+4) (y-1) = 0

either (9y+4) = 0, y =-(4/9)
or (y-1) = 0, y= 1

when y =-(4/9)
x = 3.5

when y =1
x = -3

note: y^2 = square of y

[Herbie]

koguma:

Herbie:

xy+y+2= 0 and 2x+9y-30. Can advise how ro solve this simult eqn? Tq

Think more you type, more you confuse on the part 2
Assume the 2 equations are
xy+y+2= 0 -- (1)
2x+9y-3=0 -- (2)

From (2), make x the subject,
2x = 3-9y
x = (3-9y) / 2 -- (3)

Put (3) into (2),
[(3-9y) / 2][y] + y +2 =0
[(3y-9y^2 ) /2 ]+y +2 = 0
3y - 9y^2 +2y +4 = 0
9y^2 - 5y - 4 =0
(9y+4) (y-1) = 0

either (9y+4) = 0, y =-(4/9)
or (y-1) = 0, y= 1

when y =-(4/9)
x = 3.5

when y =1
x = -3

note: y^2 = square of y

Thanks! Thanks!
Ds tried using y=-xy-2 into eqn 2 and couldn't solve it.

[koguma]

Herbie:

Thanks! Thanks!
Ds tried using y=-xy-2 into eqn 2 and couldn't solve it.

When you make \"y\" the subject, i.e. \"y\" appears on the left hand side of the equation, the right hand side cannot have y.

Hence you cannot have y = -xy-2 since the \"y\" appears on both side of the equation.

[Herbie]

Hi koguma! Many thanks for yr explanation!