It is known that the sum of 3x and X + 8 is 28, then x = (), 4x-8.8 = ()

It is known that the sum of 3x and X + 8 is 28, then x = (), 4x-8.8 = ()

It is known that the sum of 3x and X + 8 is 28, then x = (5), 4x-8.8 = (11.2)

M + n = 3, find the square of 2m + the fifth power of 4mn-2n-6

The title is wrong. It should be 2n to the second power
2m^2＋4mn＋2n^2－6
=2*（m^2＋2mn＋n^2）-6
=2*（m+n）^2-6
=2*9-6
=12

If M is the root of the equation AX2 + BX + C = 0 about X, then the quadratic equation with 1 / m as the root is

Substituting x = m into the equation is: am & sup2; + BM + C = 0
Two sides of the equation are multiplied by 1 / M & sup2; where a + B / M + C / M & sup2; = 0
That is: C * (1 / M) & sup2; + b * (1 / M) + a = 0
The equation is: CX & sup2; + BX + a = 0