Question

Wielomian W(x)= ax^2-7x+1. Oblicz a gdy W (2)= -21

Answer 1

W(x)= ax^2-7x+1
W(2)= -21

W(2)=a×2²-7×2+1=-21
4a-14=-22
4a=-8
a=-2

Answer 2

-21=2*2a-7*2+1
-21=4a-14+1
-21=4a-13
-21+13=4a
-8=2a/:2
a=-4