Tim's Responses in WyzAnt Answers

There is no need to assume the expression is equal to zero.  

Instead assuming the expression is equal to an unknown y will be your best analytical guide for future advanced math classes including calculus.

2x^2 - 9x + 4 is factorable to (2x-1)(x-4) as my fellow tutors have already expounded upon.

Analytically, it's an upward parabola since there is a positive x^2 included in the expression.

If the base of the parabola is above the x axis then, then y will never equal zero so bad bad bad assumption.

Calculus is your best analytical tool.  When you calculate dy/dx and set the result equal to zero, you will find the x value of the base of the parabola.  

dy/dx = (4x - 9) = 0, and thus the line x = 2.25 sits on the extreme base of the upward parabola.  

When y = (2x-1)(x-4) and you plug in x, you'll get y = (3.5)(-1.75) = -6.125

So the base of the parabola is located at (2.25, -6.125) where the y value of the upward parabola's extreme base is below the x axis.

Only now can you conclude there are two points on y where the parabola touches the x-axis.  

There are an infinite many points along the parabola, but x = 4 and x = 1/2 when y = 0 are usually of interest.  

I intentionally do not say 'or', but rather I say 'and' because of definitive conclusion there are two points where the parabola touches the x-axis (also known as when y = 0)

Khalid,

What if you rewrote it like this:

         116x - 2y - 4z + 2 = 1

 +       - 1x +2y - 2z + 0 = 1

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the best you can do is simplify the answer as z(x)

I don't want to cheat and give you the answer, but it will look like this below:

z(x) = (a number)x + (another number)

Once you find this for one of the equations, you can replace the z in the other equation with (a number)x + (another number) and then you can simultaneously solve for the z and x solutions.  Knowing z and x, you can isolate to solve for y.