Question

Calculeaza ac+bc+ad+bd stiind ca a+b=27 si c+d=30 (Prin ab intelegema*b)

Answer 1

a×c + b×c + a×d + b×d = 810

= c × ( a + b ) + d × ( a + b ) =

= ( a + b ) × ( c + d ) → am dat factor comun pe a + b

= 27 × 30 =

= 810

Answer 2

ac+bc+ad+bd = a(c+d) + b(c+d) inlocuim c+d=30 si obtinem

a*30+b*30 = 30(a+b) = 30*27 = 810 (a+b=27)