Question 117687
factor 
x^2+5x-66 
= x^2+11x-6x-66

= x(x+11)-6(x+11)

= (x+11)(x-6)

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x2-13xy+40y^2

= x^2-5xy-8xy+40y^2

= x(x-5y)-8y(x-5y)

= (x-5y)(x-8y)

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Cheers,
Stan H.