Answer:
A = -1
B = -3
Explanation:
you need to do all the multiplication on both sides and then simply compare the factors of the various powers of x.
so,
-9x² - 9×A×x + 2 = 3×B×x² + 6x -Bx - 2 + 4
-9x² - 9×A×x + 2 = 3×B×x² + (6-B)x + 2
the x-less constants 2 = 2 are correct. now we need to compare the factors for the other parts of x.
we have left and right only one expression of x²
-9x² on the left
3×B×x² on the right
therefore,
-9 = 3×B
=> B = -3
otherwise the equation would not be correct for all values of x.
the only other parts remaining are
-9×A×x = (6-B)x = (6 - -3)x = (6+3)x = 9x
=>
-9×A = 9
-A = 1
A = -1
remember, all parts of the left and of the right side must be equal for the equation to be true in all cases.