X can be anything you want as long as it is not 1 or -7. If you have repeated x values with different y values, then it won't be a function.
Positive Slope
<em>TIP for finding what slope it is:</em>
<em>Positive </em>- the line is pointing right
<em>Negative</em> - the line is pointing left
<em>Undefined </em>- the line is pointing up and down
<em>Zero</em> - the line is point from left to right
= 3(4a^2 + 4a - 3) - 4a^2 + 28
= 12a^2 + 12a - 9 - 4a^2 + 28
= 8a^2 + 12a + 19
= 4a(2a + 3) + 19
Area of a rectangular lawn = l×b
255=15×x
Hence the breadth is 17 m
Hence perimeter =2(l+b)=2(15+17)=64