Question

bài 1 giải phương trình

a, (x²+5x)² - 2(x²+5x)=24

b, (x²-x-2).(x²+x-3)=12

c,(x+2)(x+3)(x-5)(x-6)-180=0

Giúp mình với tối đi hc rồi

Answer 1

a, (x2+5x)2 - 2(x2+5x)=24

=>(x²+5x)²-2(x²+5x)-24=0

=>t²-2t-24=0

=>t=6

t=-4

=>x²⁺⁵x=6

x²+5x=-4

=>x=1

x=-6

x=-1

x=-4

b, (x2-x-2).(x2+x-3)=12

c,(x+2)(x+3)(x-5)(x-6)-180=0

=>x²+3x+2x+6).(x-5).(x-6)-180=0

=>(x²+5x+6).(x-5).(x-6)-180=0

=>(x³-19x-30).(x-6)-180=0

=>x⁴-6x³-19x²+114x-30x+180=0

=>x⁴-6x³-19x²+84x=0

=>x(x³-6x^2-19x+84)=0

=>x(x³-3x²-3x²⁺⁹x-28x+84)=0

=>x(x²(x-3)-3x(x-3)-28(x-3))=0

=>x(x-3).(x²-3x-28)=0

=>x(x-3).(x²⁺⁴x-7x-28)=0

=>x(x-3)(x.(x+4)-7(x+4))=0

=>x(x-3)(x=4)(x-7)=0

=>x=0

x-3=0

x+4=0

x-7=0

=>x=0

x=3

x=-4

x=7

Answer 2