Question

5a-5b=
(3x-1)(x+7)-(x+7)(2x-5)
4x la puterea a 2a -49
9(x+3)la puterea a2a -4x la put a 2
Mersi

Answer 1

5a-5b=5(a-b)
(x+7)(3x-1-2x+5)=(x+7)(x+4)
9(x+3)²-4x²=[3(x+3)-2x][3(x+3)+2x]= (3x+9-2x)(3x+9+2x)=(x+9)(5x+9)

O seara buna!

Answer 2

5a-5b=5(a-b)
(3x-1)(x+7)-(x-7)(2x-5)=

3x²+21x-x-7-(3x²-5x-14x+35)=
3x²+20x-7-3x²+5x+14x-35=
39x-42=0⇒39x=42⇒x=42/39⇒x=14/13
4x²-49=0
a=4
b=0
c-49
Δ=b²-4ac⇒Δ=0+196⇒√Δ=√196⇒Δ=14
x1x2=-b+-√Δ/2a=
x1=0+14/8⇒14/8⇒x1=7/4
x2=0-14/8⇒-14/8⇒x2=-7/4

9(x+3)²-4x²=
9(x²+6x+9)-4x²=
9x²+54x+81-4x²=
5x²+54x+81=0
a=5
b=54
c=81
Δ=b²-4ac⇒2916-1620=Δ=1296⇒√Δ=√1296⇒Δ=36
x1x2=-b+-√Δ/2a
x1=-54+36/10⇒18/10⇒x1=1.8
x2=-54-36/10⇒90/10⇒x2=9
sucees