Question

(X+3)²=3X(X+7)-X²-7X

Answer 1

x²+2.x.3+3²=3x²+21x-x²-7x
x²+6x+9=3x²+21x-x²-7x
x²-3x²+x²-21x+7x+6x+9=0
-x²-8x+9=0 (-1)
x²+8x-9=0
a- 1
b- 8
c- -9
b²-4.a.c
8²-4.1.-9
64+36
Δ=100
-b+-√Δ/2.a
-8+-10/2
2/2=1
-18/2=-9
a1= 1
a2= -9