Question

Solve 3x+4y=7 and 2x+y=−2 by substitution method.

Answer 1

$Given \:pair \:of \:linear \:equations :$

$3x + 4y = 7 \: ---(1) \:and \:$

$2x + y = -2 \implies y = -2 - 2x \: --(2)$

/* put y = -2 - 2x in equation (1) ,we get */

$3x+ 4(-2-2x) = 7$

$\implies 3x - 8 - 8x = 7$

$\implies - 8 - 5x = 7$

$\implies - 5x = 7 + 8$

$\implies - 5x = 15$

$\implies x = \frac{15}{-5}$

$\implies x = -3 \: --(3)$

/* Put value of x in equation (2) ,we get */

$y = -2 - 2\times (-5)$

$\implies y = -2 + 10$

$\implies y = 8$

Therefore.,

$\red {(x,y) } \green {= ( -5, 8 ) }$

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