If the image of a function y = ax + B passes through (- 2,1), then the image of a parabola y = ax2-bx + 3 passes through () A. （-2，1）B. （2，1）C. （2，-1）D. （-2，-1）

If the image of a function y = ax + B passes through (- 2,1), then the image of a parabola y = ax2-bx + 3 passes through () A. （-2，1）B. （2，1）C. （2，-1）D. （-2，-1）

Substituting the point (- 2, 1) into y = ax + B to get - 2A + B = 1, ∩ B = 2A + 1, when x = - 2, y = ax2-bx + 3 = 4A + 2B + 3, substituting B = 2A + 1 into y = 4A + 4A + 2 + 3 = 8A + 5, so option a is wrong; when x = 2, y = ax2-bx + 3 = 4a-2b + 3, substituting B = 2A + 1 into y = 4a-4a-2 + 3 = 1, so option B is correct; when x = 2

If the quadratic equation AX2 + BX + C = 0 (a ≠ 0) has two positive real roots, what relations should a, B and C satisfy?

Let two equations be X1 and X2, then X1 + x2 = - BA > 0, x1 · x2 = CA > 0, that is, a and B are different signs, a and C are the same sign. Therefore, the relationship between a, B and C should be b2-4ac ≥ 0, a and B are different signs, a and C are the same sign

If the quadratic equation AX + BX + C = 0 (a ≠ 0) has two positive real roots, what relations should a, B and C satisfy

Widal theorem X1 + x2 = - B / a > 0, B / A0, so b-4ac ≥ 0 and a and C have the same sign, a and B have the opposite sign

Given the parabola y = x2 + ax + A-2 (1), it is proved that there are always two different intersections between the parabola and the x-axis
Need process

Δ = A2-4 (A-2) = (A-2) 2 + 4 > 0
So there are always two different intersections between the parabola and the x-axis