Question

(у-7)(7у+49)=(у+8)(у-7)

Answer 1

7y²+49y-49y-343=y²-7y+8y-56
7y²-343=y²+y-56
6y²-y-343+56=0
6y²-y-287=0
D=1-4*6*(-287)=1+6888=6889
y₁=(1+83)/12=84/12=7
y₂=(1-83)/12=-82/12=-6  5/6