d) x + 2y = 3 và 2x + 3y = -1
d) {x+2y=32x+3y=−1
d) {x+2y=32x+3y=−1⇔{2x+4y=62x+3y=−1⇔{y=72x+3y=−1⇔{y=7x=−11
d) {x+2y=32x+3y=−1
d) {x+2y=32x+3y=−1⇔{2x+4y=62x+3y=−1⇔{y=72x+3y=−1⇔{y=7x=−11