` a) ` ` 3x^2 - 2x(5 + 1,5x) + 10 `
` = 3x^2 - 10x - 3x^2 + 10 `
` = (3x^2 - 3x^2) - 10x + 10 `
` = -10x + 10 `
` b) ` ` 7x(4y - x) + 4y(y - 7x) - 2(2y^2 - 3,5x) `
` = 28xy - 7x^2 + 4y^2 - 28xy - 4y^2 + 7x `
` = (28xy - 28xy) + (4y^2 - 4y^2) - 7x^2 + 7x `
` = -7x^2 + 7x `
` c) ` ` {2x - 3(x - 1) - 5[x - 4(3 - 2x) + 10]}.(-2x) `
` = {2x - 3x + 3 - 5x + 20(3 - 2x) - 50}.(-2x) `
` = {-6x - 47 + 60 - 40x}.(-2x) `
` = {-46x + 13}.(-2x) `
` = 92x^2 - 26x `