Question

f(x) = x2 + 3x
and
g(x) = x - 4
Show that fg(x) = x2 - 5x + 4

Please help, I dont wanna ask my dad. .--.​

Answer 1

Hey There

Here's The Answer

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• Given :

• f ( x ) = x² + 3x
• g ( x ) = x - 4

• To Show : f ( g(x) ) = x² - 5x + 4

=> f ( g(x) ) = f ( x - 4 )

=> f ( x - 4 ) = ( x - 4 )² + 3 ( x - 4 )

• Using ( a - b )² = a² + b² - 2ab

=> f ( x - 4 ) = ( x² + 4² - 2 × x × 4 ) + 3x - 12

=> f ( x - 4 ) = x² + 16 - 8x + 3x - 12

=> f ( x - 4 ) = x² - 5x - 4

Hence, shown.

Hope It Helps.