Mathematics
Find the value of:
(i) 2x2 - 3x + 4 when x = 2
(ii) 4x3 - 5x2 - 6x + 7 when x = 3
(iii) 3x3 + 9x2 - x + 8 when x = 4
(iv) 2x4 - 5x3 + 7x - 3 when x = 2
Answer
(i) Substituting x = 2 in the given expression, we get:
2x2 - 3x + 4
= 2(2)2 - 3(2) + 4
= 2(4) - 6 + 4
= 8 - 6 + 4
∴ 2x2 - 3x + 4 = 6
(ii) Substituting x = 3 in the given expression, we get:
4x3 - 5x2 - 6x + 7
= 4(3)3 - 5(3)2 - 6(3) + 7
= 4(27) - 5(9) - 18 + 7
= 108 - 45 - 18 + 7
∴ 4x3 - 5x2 - 6x + 7 = 52
(iii) Substituting x = 4 in the given expression, we get:
3x3 + 9x2 - x + 8
= 3(4)3 + 9(4)2 - 4 + 8
= 3(64) + 9(16) - 4 + 8
= 192 + 144 - 4 + 8
∴ 3x3 + 9x2 - x + 8 = 340
(iv) Substituting x = 2 in the given expression, we get:
2x4 - 5x3 + 7x - 3
= 2(2)4 - 5(2)3 + 7(2) - 3
= 2(16) - 5(8) + 14 - 3
= 32 - 40 + 14 - 3
∴ 2x4 - 5x3 + 7x - 3 = 3
Related Questions
Divide:
(a) 12x ÷ 2x
(b) 24ab ÷ 8a
(c) 9x ÷ 3y
(d) 25a2 ÷ 5a
(e) 49xy ÷ 7xy
Find the value of:
(i) 3x + 2y when x = 3 and y = 2
(ii) 5x - 3y when x = 2 and y = 5
(iii) a + 2b - 5c when a = 2, b = 3 and c = 1
(iv) 2p + 3q + 4r + pqr when p = 1, q = 2 and r = 3
(v) 3ab + 4bc - 5ca when a = 4, b = 5 and c = 2
If x = 5, find the values of:
(i) 6 - 7x2
(ii) 3x2 + 8x - 10
(iii) 2x3 - 4x2 - 6x + 25