Respuesta :

giel

(x+4)(x-3)=30

x^2 +x -12 =30

x^2 +x =42

x^2 +x -42 =0

(i solved it by factorising: _x^2 × -42)

x^2 -6x +7x -42 =0

x(x-6) +7(x-6) 0

(x-6)(x+7)=0

x=6; x=-7

since it's a length, x can't be a negative number, so it must be 6

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