WAEC - Mathematics (2016 - No. 11)
Given that 2x + y = 7 and 3x - 2y = 3, by how much is 7x greater than 10?
1
3
7
17
Açıklama
2x + y = 7...(1)
3x - 2y = 3...(2)
From (1), y = 7 - 2x for y in (2)
3x - 2(7 - 2x) = 3
3x - 14 + 4x = 3
7x + 3 + 14 = 17
x = \(\frac{17}{7}\)
Hence, 7 x \(\frac{17}{7}\)
= 17 - 10
= 7
3x - 2y = 3...(2)
From (1), y = 7 - 2x for y in (2)
3x - 2(7 - 2x) = 3
3x - 14 + 4x = 3
7x + 3 + 14 = 17
x = \(\frac{17}{7}\)
Hence, 7 x \(\frac{17}{7}\)
= 17 - 10
= 7