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VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematical Methods CAS => Topic started by: mathsfailure on February 27, 2018, 07:26:01 pm

Title: Methods question HELP!
Post by: mathsfailure on February 27, 2018, 07:26:01 pm: Please help!

A quadratic rule for a particular parabola is of the form y = ax2 + bx. The parabola passes through the point with coordinates (−1,4) and one of its x-axis intercepts is 6. Find the values of a and b.
Title: Re: Methods question HELP!
Post by: GMT. -_- on February 27, 2018, 07:36:29 pm: Just create two equations from the given info and solve simultaneously and you'll get your 2 values.
1 - 0=36a+6b
2 - 4=a-b
Title: Re: Methods question HELP!
Post by: mathsfailure on February 27, 2018, 07:44:44 pm: Thanks!
Title: Re: Methods question HELP!
Post by: mathsfailure on February 27, 2018, 07:46:51 pm: Got one more

A quadratic rule for a particular parabola is of the form y = a(x−b)2 + c. The parabola has vertex (1,6) and passes through the point with coordinates (2,4). Find the values of a, b and c.
Title: Re: Methods question HELP!
Post by: PolySquared on February 27, 2018, 07:48:24 pm: You need to create two similtaneous equations by substituting in you given values in place of the x and y variables:

$4 =a-b$
$0 = 36a + 6b$

You can enter this on your CAS by pressing menu - 3,7,1 - or just solve it by hand. I hope this helps ;D
Title: Re: Methods question HELP!
Post by: PolySquared on February 27, 2018, 07:53:01 pm: Quote from: mathsfailure on February 27, 2018, 07:46:51 pm
Got one more

A quadratic rule for a particular parabola is of the form y = a(x−b)2 + c. The parabola has vertex (1,6) and passes through the point with coordinates (2,4). Find the values of a, b and c.

Start by creating an equation using the turning point information provided:

$y = a(x-1)^2+6$

Then substitute the other coordinates of (2,4) into the place of x and y

$4 = a(2-1)^2+6$

Now just solve for a

$4 = a+6$
$a=2$

Now just place the value of a back into the original equation

$y=2(x-1)^2+6$

Hope this helps ;D
Title: Re: Methods question HELP!
Post by: mathsfailure on February 27, 2018, 07:59:23 pm: Thank you so much for your help!