Explanation:
Find the product, sum and factors which are P=56, S=15 and F=8,7 respectively.
r²+15r+56=0
replacing with the factors in the equation
=> r²+8r+7r+56=0
r(r+8)+7(r+8)=0
(r+8)(r+7)=0
=> r= –8 and –7
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