Question

4. Evaluate the following:
(1) 2a + 3b - c if a = 3, b = - 4, C = -2
(ii) a + b3 + c3 - 3abc if a = - 1, b = 2, c = 3
(iii) a + b3 + 3ab² + 3a²b if a = 2, b = -3
(iv) 5 + a² + ab - 9c if a = 5, b = 4, c = 0
(v) 6a - 5b2 + 2c- 3a²bc if a = 1, b = 2, c = -1​

Answer 1

(1)= (2×3)+{3×-4-(-2)}

= 6+{3×-4+2}

= 6+{3×-2}

= 6+(-6)=0

(2)= (-1)+(2×3)+(3×3)-{3×(-1)×2×3}

= (-1)+6+9-{-18}

= -1+6+9+18= 32

(3)= 2+(-3×3)+{3×2×(-3)²}+{3×2²×(-3}

= 2+(-9)+{6×9}+{12×(-3)}

= 2-9+54+(-36)

= 2-9+54-36

= 2+54-9-36

= 56-45= 11

(4)= 5+5²+(5×4)-(9×0)

= 5+25+20-0= 50

(5)= (6×1)-(5×2×2)+{2×(-1)}-{3×1²×2×(-1)}

= 6-20+(-2)-(-6)

= 6-20-2+6

= 6+6-20-2

= 12-22= -10