Question 221303
Can you solve this problem


Factorise


{{{15+15x-20x^2}}}


Step 1.  Factor out -5 and rearrange in descending order


{{{15+15x-20x^2= -5(4x^2-3x-3)}}}  ANSWER


Step 2.  Now work with the terms in the parenthesis.  We need two integers m and n whose sum is -3 and whose product m*n=(-3)(4)=-12.


Step 3.  After trial and error there are no integers that satisfies the quadratic equation.


Step 4.  Use the quadratic formula given below for the equation {{{4x^2-3x-3}}}


{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}


where a=4, b=-3, and c=-3


*[invoke quadratic "x", 4, -3, -3 ]



Step 5.  ANSWER:  {{{15+15x-20x^2= -5(4x^2-3x-3)}}} and we could use the quadratic equation to factor out the quadratic terms as found in step 4.


I hope the above steps were helpful.


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Good luck in your studies!


Respectfully,
Dr J