1 )
H = ( x - 5 )( x + 1 ) + ( x - 5 )(2x - 3 )
= ( x² + x - 5x - 5 ) + ( 2x² - 3x - 10x + 15 )
= 3x² + 3x + 10
2 )
H= ( x - 5 )( x + 1 + 2x - 3 )
= ( x - 5 )( 3x - 2 )
a ) x = 0
H = ( 0 - 5 )( 3 × 0 - 2 )
= 10
b )
x = 5
H ( 5 - 5 )( 3 × 5 - 2)
= 0 × 13
= 0
c )
H = 0
( x - 5 )( 3x - 2 ) = 0
x - 5 = 0 ou 3x - 2 = 0
x = 5 ou x = 2/3
Sℝ = { 2/3 ; 5 }