Question 1053226
h= -0.2x^2+1.75x+7.  Graph it to get a sense of what is going on.
{{{graph(300,300,-10,12,-10,12,-0.2x^2+1.75x+7)}}}
h(x)=4.25
4.25=-0.2x^2+1.75x+7
0=-0.2x^2+1.75x+2.75
x=-(1/0.4) (-1.75)-sqrt(3.0625-4(-0.2)(2.75)); sqrt term is 5.2625=2.37
x=-2.5*(-4.125)=10.3 cm
Note: here, you use the negative sqrt, since the leading coefficient is negative, 1/2a is negative as well.  One can check by using the positive square root, and that will give rise to a negative x-value on the parabola.  It is -1.55 cm, which is consistent with the graph.

One may bypass all of this by changing all the signs and treating it as a typical positive x^2 quadratic equation.