Rewrite the two equation here ... 2x + 2y = 42 ---------- (1) xy = 80 ----------------- (2)
From (2): xy = 80 x = 80/y ------- Sub into (1) 2(80/y) + 2y = 42 160/y + 2y = 42 Divide by 2 for every term 80/y + y = 21 multiply by y for every term 80 + y² = 21y rearrange y²-21y+80 = 0 (y - 16)(y - 5) = 0 y = 16 or y = 5 --------- sub into (2)
