9x2-155x-500 factorise by quadratic formula.
Answers
Step-by-step explanation:
Find the roots means to solve for x.
9x2 - 155x - 500 = 0
We can use the AC method. This is similar to factoring by grouping.
Find the product of the coefficient of x2 and the constant term.
(9)(-500) = -4500
Now find two numbers that multiply to -4500 and add to -155. This tells us that one number is positive while the other is negative.
25 and -180 works. These numbers add up to -155
So now we can write the equation as
9x2 + 25x - 180x - 500 = 0
Rearrange the terms so that the terms that have common factors are together.
9x2 - 180x + 25x - 500 = 0
9x(x - 20) + 25(x - 20) = 0
The common factor in the grouping is (x - 20).
(x - 20)(9x + 25) = 0
Now use set the factors equal to zero and solve for x from the two parts.