(7 – 2x) × (2x – 7) = …

(7 – 2x) × (2x – 7) = …

Cara Penyelesaian

(7 – 2x) × (2x – 7) = 7(2x – 7) – 2x (2x – 7)

= (7(2x) – 7(7)) + (-2x(2x) – 2x(-7))

= (7)(2)x – 49 + (-2)(2)(x)(x) + (-2)(-7)x

= 14x – 49 – 4x² + 14x

= – 4x² + 14x + 14x – 49

= – 4x² + (14 + 14)x – 49

= – 4x² + 28x – 49