tolong ya pke cara!!!

a.
= (10 × 2y) - (10 × 10)
= (10 × 2)y - 100
= 20y - 100

b.
= (x × 5x) + (x × (-1)) + (5 × 5x) + (5 × (-1))
= 5x² + (-x) + 25x + (-5)
= 5x² + (-1 + 25)x - 5
= 5x² + 24x - 5

c.
= (7 × 2x) + (7 × (-7)) + (-2x × 2x) + (-2x × (-7))
= 14x + (-49) + (-4x²) + 14x
= -4x² + (14 + 14)x - 49
= -4x² + 28x - 49