Evaluate by two methods.

Question

Philoid · Accepted Answer

I. Expanding along the first row

= 2(1×1 – 4×(–2)) – 3(7×1 – (–2)×(–3)) – 5(7×4 – 1×(–3))

= 2(1 + 8) – 3(7 – 6) – 5(28 + 3)

= 2×9 – 3×1 – 5×31

= 18 – 3 – 155

= –140

II. Expanding along the second column

= 2(1×1 – 4×(–2)) – 7(3×1 – 4×(–5)) – 3(3×(–2) – 1×(–5))

= 2(1 + 8) – 7(3 + 20) – 3(–6 + 5)

= 2×9 – 7×23 – 3×(–1)

= 18 – 161 +3

= –140