solve the following (x+3)(x+7)
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Answered by
1
Answer:
(x+3)(x+7)
x^2+7x+3x+21
x^2+10x+21
Answered by
3
Step-by-step explanation:
(x+9)(x−3)(x−7)(x+5)=385
{(x+9)(x−7)}{(x+5)(x−3)}=385
(x
2
+9x−7x−63)(x
2
+5x−3x−15)=385
(x
2
+2x−63)(x
2
+2x−15)=385
Put x
2
+2x=t
(t−63)(t−15)=385
t
2
−15t−63t+945=385
t
2
−78t+560=0
t
2
−8t−70t+560=0
t(t−8)−70(t−8)=0
(t−70)(t−8)=0
t=70,8
x
2
+2x=70
x
2
+2x−70=0.........(i)
x
2
+2x=8
x
2
+2x−8=0........(ii)
Solving (i)
x
2
+2x−70=0
Using quadratic formula
x=
2
−2±
4−4(1)(−70)
=
2
−2±
284
x=
2
−2±2
71
=−1±
71
Solving (ii)
x
2
+2x−8=0
x
2
+4x−2x−8=0
x(x+4)−2(x+4)=0
(x−2)(x+4)=0
x=2,−4
∴ The values of x are 2,−4,−1+
71
and −1−
71
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