How to solve 3x + 60 = 4.5X + 90

How to solve 3x + 60 = 4.5X + 90

3x+60=4.5x+90
4.5x-3x=60-90
1.5x=-30
x=-20

The solution of x-4-6 / 5x = 1 / 3x-2 is

x－4－6/5x=1/3x－2,
-8/15x=2,
x=-15/4

If a = 3x ^ 2 - X-1, B = 4x ^ 2-5x + 4, then a and B have the same size

A-B
=3x^2 -x-1-(4x^2-5x+4)
=3x^2 -x-1-4x^2+5x-4
=-x^2+4x-5
=-(x^2-4x+4)-1
=-(x-2)^2-1

Compare the size of 5x ^ 2-4x and 3x ^ 2-4x-6
With format·

5x^2-4x-(3x^2-4x-6)
=5x ^ 2 + 6 because 5x ^ 2 is non negative, 5x ^ 2 + 6 is greater than 0
So 5x ^ 2-4x is greater than 3x ^ 2-4x-6

1.01×0.99=?

1.01×0.99=(1+0.01)(1-0.01)=1-0.01^2=0.9999

What is 0.01 to 0.99

=(0.01+0.99)+(0.02+0.98)+…… +(0.49+0.51)+0.50
=1+1+…… +1+0.50
=1×49+0.50
=49.5

0.91*99+91*0.01
To use a simple algorithm Oh~

0.91*99+91*0.01
=0.91*（100-1）+0.91
=0.91*（100-1+1）
=0.91*100
=91

48 × 101-48 is easy to calculate,

38 × 101 =, which is a simple calculation

38*（100 + 1）
= 3800 + 38
=3838

Simple calculation of 38 × 101 + 385

38×101＋385=38×100+38×1+38×10+5=3800+380+38+5=4180+43=4223