+0

# need assistance!

+1
48
2
+798

Find a+b+c, given that \begin{align*} ax+by+c&=x+7,\\ a+bx+cy&=2x+6y,\\ ay+b+cx&=4x+y. \end{align*}

Jul 8, 2020

#1
+8336
0

$$(a + b + c)(1 + x + y) = 7(1 + x + y)$$

which means a + b + c = 7 if $$x + y \neq -1$$.

(The formula is easily verifiable by expanding the terms and comparing to what you have after adding the three equations.)

Jul 8, 2020
edited by MaxWong  Jul 8, 2020
#2
+798
0

Thanks!

AnimalMaster  Jul 8, 2020