Simple mathematical expression of coefficient n^2－4＝a（n－1）（n－2）+b（n－1）＋c

Simple mathematical expression of coefficient n^2－4＝a（n－1）（n－2）+b（n－1）＋c

It's time to tidy up
(1-a)n^2+(3a-b)n+(-2a+b-c-4)=0
be
1-a=0
3a-b=0
-2a+b-c-4=0
That is, a = 1, B = 3, C = - 3

When tanxa is equal to 3, find the value of COS square a minus 3sinacosa

tana=3
cos^2a-3sinacosa
=(COS ^ 2a-3sinacosa) / (sin ^ 2A + cos ^ 2a), [numerator and denominator divide by cos ^ 2A]
=(1-3tana)/(tan^2a+1)
=(1-9)/(9+1)
=-4/5

It is known that x = 1, y = 2 is a solution of the quadratic equation 3x + ay = - 1, and the value of a is obtained
The format must be correct! I know how to do it,

Substituting the value of the solution into the equation, we get the following result:
3×1+2a=-1
3+2a=-1
a=(-1-3)÷2
a=-2

What does (4.38-1.36) divide by 1.3 + 0.04 mean

(4.38-1.36) divided by 1.3 + 0.04
What is the sum of the difference between 4.38 and 1.36 divided by the quotient of 1.3 and 0.04?

3 (4x-2) - 2 (2 + x) = 25, solve the equation!

3(4x-2)-2(2+x)=25
12x-6-4-2x=25
10x-10=25
10x=25+10
10x=35
x=3.5

39.7 * 40.3 =? (calculated by square difference formula)

The original formula = (40-0.3) (40 + 0.3) = 40 square-0,3 square = 1600-0.09 = 1599.97

In the triangle ABC, we know that 2B = a + C, and prove that 2sinb = sinc + Sina

Sine theorem
a/sinA=b /sinB=c /sinC

Calculate 1234 + 2341 + 3412 + 4123=______ ．

1234 + 2341 + 3412 + 4123, = (1111 + 123) + (2222 + 119) + (3333 + 79) + (4444-321), = 1111 + 2222 + 3333 + 4444 + (123 + 119 + 79-321), = 1111 + 2222 + 3333 + 4444, = 1111 × (1 + 2 + 3 + 4), = 1111 × 10, = 11110

It is known that the vertex of parabola C1: y = - x2 + 2mx + 1 (M is constant, and m ≠ 0) is a, intersecting with y axis at point C; parabola C2 and parabola C1 are symmetric about y axis, and their vertex is B. if point P is a point on parabola C1, such that the quadrilateral with a, B, C and P as vertex is diamond, then the value of M is______ ．

From the parabola C1: y = - x2 + 2mx + 1, we know that points a (m, M2 + 1), C (0, 1); ∵ the parabola C1, C2 are symmetric about the Y axis, ∵ the points a, B are symmetric about the Y axis, then ab ∥ the X axis, and B (- m, M2 + 1), ab = | - 2m |; if the quadrangle with a, B, C, P as the vertex is rhombic, then & nbsp; ab ∥ CP; in the parabola C1: y = - x2 + 2mx + 1, ab = | - 2m |

Please explain the factorization of mathematics in grade one, thank you! (18 19:33:42)
 
（2a-b)2-2a+b

(2a-b)2-2a+b =(2a-b)2-(2a-b ) =(2a-b)(2a-b-1)