1. (a+3b)(2a-4b) 2.(5+a)(7-a) 3.(5m-1)(2m+4)

Matematika
Persamaan Kuadrat VIII SMP

Pembahasan :
(a + 3b)(2a - 4b)
= a.2a + a.(-4b) + 3b.2a + 3b.(-4b)
= 2a² - 4ab + 6ab - 12b²
= 2a² + 2ab - 12b²

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(5 + a)(7 - a)
= 5.7 + 5.(-a) + (a)(7) + (-a)(a)
= 35 - 5a + 7a - a²
= -a² + 2a + 35

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(5m - 1)(2m + 4)
= (5m)(2m) + (5m)(4) + (-1)(2m) + (-1)(4)
= 10m² + 20m - 2m - 4
= 10m² + 18m - 4

=> (a + 3b) (2a - 4b)
=> 2a^2 - 4ab + 6ab - 12b^2
=> 2a^2 + 2a - 12b^2


=>(5 + a )(7 - a )
=> 35 - 5a + 7a - a^2
=> 35 + 2a - a^2
=> -a^2 + 2a + 35



=> (5m - 1)(2m + 4)
=> 10m^2 + 20m - 2m - 4
=> 10m^2 + 18m - 4