Question

daca x+y=17,x+z=28,y+z=15,calculati xy+xz+15y

Answer 1

Le adunam
x+ y+ x+z+y+ z= 17+28+15
2+ 2y+2z= 60
2×( x+y+z) = 60
x+y +z= 60:2
x+ y+ z= 30
x+y= 17 =>z= 30 -17 => z= 13
y+ z=15 => x= 30-15=> x= 15
x+z= 28 => y= 30-28=> y= 2


x×y+ x×z+ 15×y =
= 15 ×2 + 15× 13 + 15×2=
= 30 + 195 + 30 =
= 255

Sper ca te.am ajutat!