Answer:x={-1,5}PREMISESy=x^2-4x-5=0ASSUMPTIONSLet x=the (unknown) independent variable by which thedependent variable y=0 is returnedCALCULATIONSy=x^2-4x-5=0Solve for x by factoring if possible or if not, then use the “quadratic formula” x=[-b +/- √(b^2-4ac)]/2a which can be used to solve any polynomial of the form ax^2 +/- bx +/- c, where a, b, and c are coefficients.The polynomial can be factored:x^2-4x-5=0 yields(x+1)(x-5)=0and,Either x=-1 or x=5 or bothTest the roots (-1,5) for validity by plugging each root into the original statement x^2-4x-5=0:If x={-1,5}, then the equations(1) (-1)^2–4(-1)-5=01-(-4)-5=0(1+4)–5=05–5=0 and0=0And,(2) 5^2–4(5)-5=0(25–20)–5=0(5–5)=0 and0=0 prove the roots (zeroes)x={-1,5} of the statement x^2-4x-5=0
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