Take half of the coefficient of x: It is 3, and half that is 3/2.
Then <span>x^2+3x=6 becomes:
</span><span> x^2+3x + (3/2)^2 =6 + (3/2)^2, and
(x+3/2)^2 = 6 + 9/4
You were not asked to solve the equation, but why not do it for the practice?
</span>Solve (x+3/2)^2 = 6 + 9/4 for x. There will be 2 values.
This is the concept of trigonometry, the height of the ramp will be given by:
sin theta=[opposite]/[hypotenuse]
theta=30
opposite=x
hypotenuse=40 ft
hence;
sin 30=x/40
thus;
x=40sin30
x=20 ft
the ramp is 20 ft high
