Question 880102
The easier one, {{{16t^2=9}}}
{{{t^2=9/16}}}
{{{t=0+- sqrt(9/16)}}}
{{{highlight(t=0+- (3/4))}}}


The less easy one, {{{x^2+5x-14=0}}}, you want to solve by graphing, then what skills you you want to use?  Do you need two-D cartesian system, or just a number line?


This appears factorable.
{{{(x+7)(x-2)=0}}}, and this has no slope to use, depending on what you want to do with a slope.  


If you want to try a set of x values and test for either truth or resulting sign to find truth as the target, this could bring you near to the answers, but factoring the quadratic, and then showing the one-dimensional graph would be simplest.  Critical values are x=-7 and x=2.  You would find that these are points to fill on the number line and each makes the quadratic equation true.

{{{number_line(450,-10,5,-7,2)}}}