Which pair of ratios is proportional?
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2x - 3y = - 13
the equation of a line in standard form is
Ax + By = C ( A is a positive integer and B, C are integers )
First obtain the equation in slope-intercept form
y = mx + c ( m is the slope and c the y-intercept )
calculate m using the gradient formula
m = ( y₂ - y₁ ) / (x₂ - x₁ )
with (x₁, y₁ ) = (1, 5 ) and (x₂, y₂ ) = (- 2, 3 )
m = =
=
y = x + c ← partial equation
to find c substitute either of the 2 points into the partial equation
using (1, 5 ), then
5 = + c ⇒ c =
rearrange the equation into standard form
multiply through by 3
3y = 2x + 13 ( subtract 3y and 13 from both sides )
2x - 3y = - 13 ← in standard form
Change the function into vertex form:
f(x)=x²-10x+16
make a square by (adding half of -10)², which is 25, then subtract it:
f(x)=x²-10x+25-25+16
f(x)=(x-5)²-9
so the vertex is at (5,-9)
another way to do it:
f(x)=x²-10x+16
the vertex is when x=-
, b=-10, a=1 in this case.
x=-(-10/2*1)=5
plug x=5 into the quadratic function, you get f(x)=-9
f(x)=x²-10x+16
make a square by (adding half of -10)², which is 25, then subtract it:
f(x)=x²-10x+25-25+16
f(x)=(x-5)²-9
so the vertex is at (5,-9)
another way to do it:
f(x)=x²-10x+16
the vertex is when x=-
x=-(-10/2*1)=5
plug x=5 into the quadratic function, you get f(x)=-9