X+4=89

X+4=89

x=85

80÷(x+9)=4
solve equations

80÷(x+9)=4
Solution x + 9 = 80 △ 4
x+9=20
x=20-9
x=11

1988+1989×19871988×1989−1=______ ．

1988 + 1989 × 19871988 × 1989 − 1, = 1988 + 1989 × (1988 − 1) 1988 × 1989 − 1, = 1988 + 1989 × 1988 − 19891988 × 1989 − 1, = 1988 × 1989 − 11988 × 1989 − 1, = 1

What's 90 and 1 / 88 times 1 / 89

=(89+89/88)×1/89
=89×1/89+89/88×1/89
=1+1/88
=1 and 1 / 88

（89+90+88+90+85+96+90+87+90+88+88+90+88+86+87+88+86）÷20=?

=[(85+86+87+88+89+90)+(86+87+88+)+(3*88+4*90+96)]÷20
=(525+261+284+360+96)÷20
=(1050+350+360)÷20
=1710÷20
=171/2

In the triangle ABC, A.B is the two roots of the equation 2x & sup2; - 5x + 2 = 0, and ∠ C = 120 ° then the edge C =?

Weida theorem a + B = 5 / 2Ab = 1A + B = 5 / 2A & # 178; + 2Ab + B & # 178; = 25 / 4A & # 178; + B & # 178; = 25 / 4-2a & # 178; + B & # 178; = 17 / 4 cosine theorem C & # 178; = A & # 178; + B & # 178; - 2abcosc = 17 / 4 + 2 * (1 / 2) = 17 / 4 + 1 = 21 / 4C = √ 21 / 2

In the triangle ABC, the lengths of edges a and B are the two roots of the equation x-5x + 2 = 0, C = 120 °, then edge C =?

The square of X - 5x + 2 = 0
The results of Weida's theorem are as follows
a+b=5
ab=2
a+b=(a+b)-2ab=21
The cosine theorem is as follows
c=a+b-2abcosC
=21-2=19
c=√19

In the triangle ABC, given that C = 120 degrees, a and B on both sides are the two roots of the equation x ^ 2-3x + 2 = 0, then the value of C on the third side is?

A and B on both sides are the two roots of the equation x ^ 2-3x + 2 = 0, and a = 1 and B = 2 can be deduced
C = 120 according to the cosine law, A2 + b2-2abcosc = C2 can deduce C = 2

In △ ABC, given the angle c = 120 degrees, both sides a and B are two of the equations x ^ 2-11x + 30 = 0, then C is equal to?
Please give the process of solving the problem,

A = 5 B = 6 cosine theorem C ^ 2 = a ^ 2 + B ^ 2-2abcosc

It is known that the solution of X + 1 / x = C + 1 / C (C is not equal to 0) is x = C or x = 1 / C. what is the solution of the equation x + 1 / (4x-6) + (a ^ 2 + 3A + 1) / 2A

Ask: is the title wrong? What is the solution of the equation x + 1 / (4x-6) + (a ^ 2 + 3A + 1) / 2A? What is the equal sign of this equation? Is the title like this? If it is: x + 1 / (4x-6) = A / 2 + 3 / 2 + 1 / (2a), multiply both sides by 2: 2x + 1 / (2x-3) = a + 3 + 1 / a2x-3 + 1