How do I solve y=2x^2 by graphing using quadratic function?

Question

How do I work it out?

Answer 1

To graph a function pick some points for x and calculate what y is equal to 

 

When x = -2 then y = 2*(-2)^2 = 2*4 = 8

When x = -1 then y = 2*(-1)^2 = 2*1 = 2

When x = 0 then y = 2*(0)^2 = 2*0 = 0

When x = 1 then y = 2*(1)^2 = 2*1 = 2

When x = 2 then y = 2*(2)^2 = 2*4 = 8 

 

Now plot the points (-2,8), (-1,2), (0,0), (1,2) and (2,8) on graph paper and draw a smooth curve thru the points.  If you know what the quadratic function y = x^2 looks like then you will see that y=2x^2 is very similar to it, just stretched in the vertical direction.  If you don't know what y = x^2 looks like then you may need to plot a few more points, like x = 3 and x = -3.