Here is a question from Edexcel GCSE Maths mock exam Jan 2024:
On the grid draw the graph of y=x^3-3x+2 for values of x from -2 to 2
By drawing a suitable straight line on the grid, use your graph to find an estimate for the solution of
2x^3-3x+4=0
Give your answer correct to 1 decimal place
I rearranged equation 2 to give equation 1 on the left hand side, as follows:
x^3-3x+2=-x^3-2
I was expecting this to give a linear equation on the right hand side not a cubic
So plotting the graphs of y=x^3-3x+2 and y=-x^3-2 should give a solution to equation 2
And it does. These two graphs intersect at x=-1.6 which is roughly the solution to equation 2.
But y=-x^3-2 is not a straight line.
Any ideas what straight line they are after??
It’s GCSE so shouldn’t be too complex
Thanks