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What two numbers add up to 9 and multiply to -90?

Sagot :

You solve the equation : t^2 - 9t - 90 = 0 ;
Δ = ( - 9 )^2 - 4 * 1 * ( - 90 ) = 81 + 360 = 441 ;
t1 = ( 9 + [tex] \sqrt{441} [/tex]) / 2 = 30 / 2 = 15 ;
t2 = ( 9 - [tex] \sqrt{441} [/tex]) / 2 = -12 / 2 = - 6 ;

The numbers are 15 and - 6 ;