Solve the equations using elimination method:
$5 a + 8 b = 9$ and $2 a + 3 b = 4$

(5, -2)

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(5, 2)

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(-5, -2)

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(-5, 2)

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Solution

The correct option is B (5, -2)
$5 a + 8 b = 9$ ----- (1)
$2 a + 3 b = 4$ ----- (2)
Multiply equation (1) by 5 and equation (2) by 2, then subtract the equation (3) and (4)
$10 a + 16 b = 18$ ----- (3)
$10 a + 15 b = 20$ ----- (4)
(-) (-) (-)
_______________
$b = - 2$
$b = - 2$
Put the value of b in equation (2), we get
$2 a + 3 b = 4$
$2 a + 3 (- 2) = 4$
$2 a = 4 + 6$
$a = \frac{10}{2}$
$a = 5$
Therefore the solution is (5, -2)

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Similar questions

- x + 2 y = 5

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