How do I graph y = 2x squared -7?
Hard to believe your text has no examples of quadratic functions. In any case, excellent graphing help can be obtained at
http://rechneronline.de/function-graphs/
In any case, graph it the same way you would any function. Pick a value for x, calculate y, and plot the point (x,y). Repeat until you get an idea of the shape of the curve.
Which values would be most adequate?
Which values should I use?
come on. Pick small values like -2,-1,0,1,2 where you can easily calculate y.
Just like you did when you were graphing lines in the beginning. You can use values like 2.83 or 5/17 or whatever, but it makes calculation a bit of a chore.
by this time you may know that parabolas have an axis of summetry. x-values equally distant from that axis produce the same y values.
For example, you know that 2x^2-7 is symmetric about the y-axis, because x^2 is always positive, whether x is positive or negative.
So, if you plot y for x=1, you automatically get y for x = -1.
To graph the equation y = 2x^2 - 7, you can use the following steps:
Step 1: Choose a range of x values to plot on the graph. For example, you can choose a range from -5 to 5.
Step 2: Substitute the selected x values into the equation to find the corresponding y values. For example, when x = -5, y = 2(-5)^2 - 7 = 2(25) - 7 = 50 - 7 = 43. Similarly, when x = 0, y = 2(0)^2 - 7 = 0 - 7 = -7.
Step 3: Plot the obtained (x, y) pairs on the graph. For example, when x = -5, y = 43, you plot the point (-5, 43). Do this for all the x values you selected in Step 1.
Step 4: Once you have plotted all the points, connect them with a smooth curve that represents the graph of y = 2x^2 - 7.
Remember, the shape of the graph will be a parabola, because the equation is in the form y = ax^2 + bx + c, where a = 2, b = 0, and c = -7. The coefficient "2" in front of the x^2 term determines the 'steepness', or how slender or fat the parabola is.
I hope this helps you graph y = 2x^2 - 7!