(ax-b)？ Sum of coefficients:

Let x= 1 and S=(a-b)?

(ax+b)？ Sum of coefficients:

Let x= 1 and S=(a+b)?

or

By solving the equations, we can get: a 1=4 and d=-2.

So bn=2(n- 1)

Let the sum of the first n terms of bn be t n.

Then Tn=n(n- 1)

So T5=20.

High school mathematics includes

Functions (quadratic function, trigonometric function, exponential function, logarithmic function, power function, inverse function, etc. ), series, solving triangle problems, vectors, inequalities, plane and solid geometry, analytic geometry (straight lines, circles, ellipses, hyperbolas, parabolas, etc.), permutation and combination, parametric equations, sets and simple logic, polar coordinates, complex numbers, etc. , although there is no algebra and geometry.